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Kamis, 26 Maret 2009

Psst! Coffee Drinkers: Fruit Flies Have Something To Tell You About Caffeine

In their hunt for genes and proteins that explain how animals discern bitter from sweet, a team of Johns Hopkins researchers began by testing whether mutant fruit flies prefer eating sugar over sugar laced with caffeine. Using a simple behavioral test, the researchers discovered that a single protein missing from the fly-equivalent of our taste buds caused them to ignore caffeine's taste and consume the caffeine as if it were not there.

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"No, you won't see jittery Drosophila flitting past your bananas to slurp your morning java anytime soon," says Craig Montell, Ph.D., a professor of biological chemistry in the Institute of Basic Biomedical Sciences at Hopkins. "The bottom line is that our mutant flies willingly drink caffeine-laced liquids and foods because they can't taste its bitterness -- their taste receptor cells don't detect it."
The Hopkins flies, genetically mutated to lack a certain taste receptor protein, have been the focus of studies to sort out how animals taste and why we like the taste of some things but are turned off by the taste of others.
By color-coding sweet and bitter substances eaten by fruit flies and examining the coloring that shows up in their translucent bellies, the Hopkins team hoped to learn whether flies missing a specific "taste-receptor" protein changed their taste preferences.
"Normally," Montell explains, "when given the choice between sweet and bitter substances, flies avoid caffeine and other bitter-tasting chemicals. But flies missing this particular taste-receptor protein, called Gr66a, consume caffeine because their taste-receptor cells don't fire in response to it."
The discovery, which is the first ever example of a protein required for both caffeine tasting and caffeine-induced behavior, will be published Sept. 19 in Current Biology.
For the study, Montell and his colleagues kept 50 fruit flies away from food overnight and for breakfast gave the starved flies 90 minutes to eat as much as they wanted of either or both of two concoctions: a blue-colored mixture of sugar and agar and a red-colored mixture of caffeine, sugar and agar. The researchers then flipped the flies onto their backs and looked at the color of their bellies to see what they ate - blue indicating a preference for eating sugar, red indicating a preference for bitter caffeine, and purple indicating no preference.
Flies missing the critical taste receptor protein Gr66a consumed the bitter caffeine solution to the same extent as the sugar-only solution. Montell and colleagues conclude that Gr66a is crucial for the normal caffeine avoidance behavior and without it, flies are seemingly indifferent to the bitter taste.
The researchers went on to examine whether this indifference to bitter was due to the taste nerves on the fly's "tongue" or some malfunction in the fly's brain. Chemical stimulants trigger taste receptor cells to send an electrical current to the brain where the information is processed and often leads to a change in behavior, such as the decision to eat or avoid.
With fine tools, the research team recorded electrical currents in those cells known to contain the Gr66a caffeine taste receptor in the fly's equivalent of the taste buds - dubbed the taste bristles.
Applying sugar to the taste bristles of normal flies, or to mutant flies missing the Gr66a protein, causes the neurons to produce electrical current "spikes" at a frequency of about 20 spikes per second. Other bitter compounds like quinine generated electrical current spikes at about the same frequency in the mutants.
Only flies missing the Gr66a taste receptor protein were unable to generate any current spikes when given caffeine. "This is a clear demonstration that Gr66a is functioning in the taste receptor cells and is not a 'general sensor' for bitter compounds, but is required more specifically for the caffeine response," says Montell.
"This indicates that flies have different receptors for the response to other types of bitter compounds," he says.
"We also tested whether the flies avoided the related bitter compounds found in tea and cocoa -- chocolate -- and found that Gr66a also is required for the response to the compound in tea, but not for the one in chocolate," he says.
Fruit flies often are used as experimental organisms because they grow quickly and are easy to manipulate genetically. Now that Montell and his colleagues have a mutant fly that is unable to taste caffeine, they hope to further examine the other genes and molecules involved in the caffeine response and better understand the biochemistry behind caffeine-induced behavior in other organisms, namely humans.
The researchers were funded by the Polycystic Kidney Disease Foundation and the National Institute of Deafness and Communicative Disorders of the National Institutes of Health.
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Like Sweets? You're More Like A Fruit Fly Than You Think

A fruit fly extends its proboscis to 'taste' a drop of sucrose. (Credit: Beth Gordesky-Gold)


According to researchers at the Monell Center, fruit flies are more like humans in their responses to many sweet tastes than are almost any other species.
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The diverse range of molecules that humans experience as sweet do not necessarily taste sweet to other species. For example, aspartame, a sweetener used by humans, does not taste sweet to rats and mice.
However, fruit flies respond positively to most sweeteners preferred by humans, including sweeteners not perceived as sweet by some species of monkeys.
The findings, published in a recent issue of the journal Chemical Senses, demonstrate the critical role of environment in shaping the genetic basis of taste preferences and feeding behavior.
"Humans and flies have similar taste responses because they share similar environments and ecological niches, not because their sweet receptors are similar genetically," notes senior author Paul A.S. Breslin, PhD, a Monell sensory geneticist. "Both are African species, both are omnivorous, and both historically are primarily fruit eaters."
To compare how molecular structure is related to sweet taste perception in humans and flies, the Monell researchers evaluated how fruit flies respond to 21 nutritive and nonnutritive compounds of varying molecular structure, all of which taste sweet to humans.
Breslin and lead author Beth Gordesky-Gold, PhD, used two behavioral tests to evaluate the flies' responses to the various sweeteners.
The taste reactivity test measures whether a fly extends its feeding tube, or 'proboscis,' to consume a given sweetener. In addition, a two-choice preference test evaluates the flies' responses to a sweetener by measuring whether they consume it in preference to a control solution (usually water).
The Monell researchers found that fruit flies and humans both respond positively to the same broad range of sweet-tasting molecules.
"The similarity between human and fly responses to sweeteners is astounding, especially in light of the differences in their taste receptors," notes Gordesky-Gold, a Drosophila (fruit fly) geneticist at Monell.
Sweet receptors belong to a large family of receptors known as G-protein coupled receptors (GPCRs), which are involved in biological processes throughout the body. Human and fly sweet taste GPCRs are presumed to have markedly different structures, an assumption that is based on differences in the genes that code for them.
Since substances will only taste sweet if they are able to bind to and activate a receptor, these two structurally different types of sweet receptors must have similar 'binding regions' that fit the same range of molecular shapes.
"That genes could be so divergent in sequence and so similar in physiology and function is truly striking," says Breslin. "This is a wonderful example of convergent evolution in perceptual behavior, where evolution has taken two different routes to address pressures imposed by shared environment and nutrition."
Future work will be directed towards modeling how these two structurally different sweet receptors could have highly overlapping sweetener affinities. Such knowledge will increase understanding of how molecules bind to GPCRs, which are targets for many pharmaceutical drugs.
The research was supported by the National Institute on Deafness and Other Communication Disorders.
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Liking Sweets Makes Sense For Kids

As any parent knows, children love sweet-tasting foods. Now, new research from the University of Washington and the Monell Center indicates that this heightened liking for sweetness has a biological basis and is related to children's high growth rate.


New research indicates that this heightened liking for sweetness has a biological basis and is related to children's high growth rate. (Credit: Copyright Joan Vicent Cantó Roig)


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"The relationship between sweet preference and growth makes intuitive sense because when growth is rapid, caloric demands increase. Children are programmed to like sweet taste because it fills a biological need by pushing them towards energy sources," said Monell geneticist Danielle Reed, PhD, one of the study authors.
Across cultures, children prefer higher levels of sweetness in their foods as compared to adults, a pattern that declines during adolescence. To explore the biological underpinnings of this shift, Reed and University of Washington researcher Susan Coldwell, PhD, looked at sweet preference and biological measures of growth and physical maturation in 143 children between the ages of 11 and 15.
The findings, reported in the journal Physiology & Behavior, suggest that children's heightened liking for sweet taste is related to their high growth rate and that sweet preferences decline as children's physical growth slows and eventually stops.
Based on the results of sensory taste tests, children were classified according to their sweet taste preference into a 'high preference' or 'low preference' group. Children in the 'low preference' group also had lower levels of a biomarker (type I collagen cross-linked N-teleopeptides; NTx) associated with bone growth in children and adolescents.
"This gives us the first link between sweet preference and biological need," said Reed. "When markers of bone growth decline as children age, so does their preference for highly sweet solutions."
Other biological factors associated with adolescence, such as puberty or sex hormone levels, were not associated with sweet preference.
"We now know that sweet preference is related to physical growth. The next step is to identify the growth-related factor that is signaling the brain to influence sweet preference," said study lead author Coldwell, Washington Dental Service Endowed Professor and Associate Professor of Dental Public Health Sciences at the University of Washington School of Dentistry.
The research was funded by a grant to the University of Washington from the National Institute of Dental and Craniofacial Research (National Institutes of Health).
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Senin, 16 Maret 2009

Biological Evolution

What is Evolution?

Biological evolution is defined as any genetic change in a population that is inherited over several generations. These changes may be small or large, noticeable or not so noticeable. In order for an event to be considered an instance of evolution, changes have to occur on the genetic level of a population and be passed on from one generation to the next. This means that the genes, or more specifically, the alleles in the population change and are passed on. These changes are noticed in the phenotypes (expressed physical traits that can be seen) of the population. A change on the genetic level of a population is defined as a small-scale change and is called microevolution. Biological evolution also includes the idea that all of life is connected and can be traced back to one common ancestor. This is called macroevolution.

What is not Evolution?
Biological evolution is not defined as simply change over time. Many organisms experience changes over time, such as weight loss or gain. These changes are not considered instances of evolution because they are not genetic changes that can be passed on to the next generation.
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Is Evolution a Theory?

Evolution is a scientific theory that was proposed by Charles Darwin. A scientific theory gives explanations and predictions for naturally occurring phenomena based on observations and experimentations. This type of theory attempts to explain how events seen in the natural world work.The definition of a scientific theory differs from the common meaning of theory, which is defined as a guess or a supposition about a particular process. In contrast, a good scientific theory must be testable, falsifiable, and substantiated by factual evidence. When it comes to a scientific theory, there is no absolute proof. It's more a case of confirming the reasonability of accepting a theory as a viable explanation for a particular event.
What is Natural Selection?

Natural selection is the process by which biological evolutionary changes take place. Natural selection acts on populations and not individuals. It is based on the following concepts:

  • Individuals in a population have different traits which can be inherited.
  • These individuals produce more young than the environment can support.

The individuals in a population that are best suited to their environment will leave more offspring, resulting in a change in the genetic makeup of a population.The genetic variations that arise in a population happen by chance, but the process of natural selection does not. Natural selection is the result of the interactions between genetic variations in a population and the environment.The environment determines which variations are more favorable. Individuals that possess traits that are better suited to their environment will survive to produce more offspring than other individuals. More favorable traits are thereby passed on to the population as a whole.

How Does Genetic Variation Occur in a Population?

Genetic variation occurs through sexual reproduction. Due to the fact that environments are unstable, populations that are genetically variable will be able to adapt to changing situations better than those that do not contain genetic variations.Sexual reproduction allows for genetic variations to occur through genetic recombination. Recombination occurs during meiosis and provides a way for producing new combinations of alleles on a single chromosome. Independent assortment during meiosis allows for an indefinite number of combinations of genes. (Example of recombination) Sexual reproduction makes it possible to assemble favorable gene combinations in a population or to remove unfavorable gene combinations from a population. Populations with more favorable genetic combinations will survive in their environment and reproduce more offspring than those with less favorable genetic combinations.

Biological Evolution Versus Creation

The theory of evolution has caused controversy from the time of its introduction until today. The controversy stems from the perception that biological evolution is at odds with religion concerning the need for a divine creator. Evolutionists contend that evolution does not address the issue of whether or not God exists, but attempts to explain how natural processes work.In doing so however, there is no escaping the fact that evolution contradicts certain aspects of some religious beliefs. For example, the evolutionary account for the existence of life and the biblical account of creation are quite different.Evolution suggests that all life is connected and can be traced back to one common ancestor. A literal interpretation of biblical creation suggests that life was created by an all powerful, supernatural being (God). Still others have tried to merge these two concepts by contending that evolution does not exclude the possibility of the existence of God, but merely explains the process by which God created life. This view however, still contradicts a literal interpretation of creation as presented in the bible.In paring down the issue, a major bone of contention between the two views is the concept of macroevolution. For the most part, evolutionists and creationists agree that microevolution does occur and is visible in nature.Macroevolution however, refers to the process of evolution that takes place on the level of species, in which one species evolves from another species. This is in stark contrast to the biblical view that God was personally involved in the formation and creation of living organisms.For now, the evolution/creation debate continues on and it appears that the differences between these two views are not likely to be settled any time soon.

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Archaea

Clusters of halobacterium strain NRC-1.NASA

Archaea:


Archaea are a group of microscopic organisms that were discovered in the early 1970s. Like bacteria, they are single-celled prokaryotes. Archaeans were originally thought to be bacteria until DNA analysis showed that they are different. In fact, they are so different that the discovery prompted scientists to come up with a new system for classifying life.


There is still much about archaeans that is not known. What we do know is that they can exist under some of the most extreme conditions, such as extremely hot, acidic, or alkaline environments.




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Three Domains:


Organisms are now classified into three Domains. The Domains are Eukaryota, Eubacteria, and Archaea.There are three main divisions of archaeans. These divisions are: Crenarchaeota, Euryarchaeota, and Korarchaeota.
Crenarchaeota:
Crenarchaeota consist mostly of hyperthermophiles and thermoacidophiles.Hyperthermophilic microorganisms live in extremely hot or cold environments.Thermoacidophiles are microscopic organisms that live in extremely hot and acidic environments. Their habitats have a pH between 5 and 1. You would find these organisms in hydrothermal vents and hot springs.

Crenarchaeota Species:
Examples of Crenarchaeotans include:
  • Sulfolobus acidocaldarius - found near volcanic environments in hot, acidic springs containing sulfur.
  • Pyrolobus fumarii - live in temperatures between 90 and 113 degrees Celsius.

Euryarchaeota:

Euryarchaeota organisms consist mostly of extreme halophiles and methanogens.Extreme halophilic organisms live in salty habitats. They need salty environments to survive. You would find these organisms in salt lakes or areas where sea water has evaporated.Methanogens require oxygen free (anaerobic) conditions in order to survive. They produce methane gas as a byproduct of metabolism. You would find these organisms in environments such as swamps, wetlands, the guts of animals (cow, deer, humans), and in sewage.


Euryarchaeota Species:

Examples of Euryarchaeotans include:

  • Halobacterium - include several species of halophilic organisms that are found in salt lakes and high saline ocean environments.
  • Methanococcus - Methanococcus jannaschii was the first genetically sequenced Archaean. This methanogen lives near hydrothermal vents.


Korarchaeota:

Korarchaeota organisms are thought to be very primitive life forms. Little is currently known about the major characteristics of these organisms. We do know that they are thermophilic and have been found in hot springs and obsidian pools.


Phylogeny:

Archaea are interesting organisms in that they have genes that are similar to both bacteria and eukaryotes. Phylogenetically speaking, archaea and bacteria are thought to have developed separately from a common ancestor.Eukaryotes are believed to have branched off from archaeans millions of years later. This suggests that archaeans are more closely related to eukayotes than bacteria.

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Drink Green Tea For Healthy Teeth And Gums

With origins dating back over 4,000 years, green tea has long been a popular beverage in Asian culture, and is increasingly gaining popularity in the United States. And while ancient Chinese and Japanese medicine believed green tea consumption could cure disease and heal wounds, recent scientific studies are beginning to establish the potential health benefits of drinking green tea, especially in weight loss, heart health, and cancer prevention.


Recent study suggests that antioxidants in green tea may help reduce periodontal disease. (Credit: iStockphoto/Ron Hohenhaus)


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A study recently published in the Journal of Periodontology, uncovered yet another benefit of green tea consumption. Researchers found that routine intake of green tea may also help promote healthy teeth and gums. The study analyzed the periodontal health of 940 men, and found that those who regularly drank green tea had superior periodontal health than subjects that consumed less green tea.
"It has been long speculated that green tea possesses a host of health benefits," said study author Dr. Yoshihiro Shimazaki of Kyushu University in Fukuoka, Japan. "And since many of us enjoy green tea on a regular basis, my colleagues and I were eager to investigate the impact of green tea consumption on periodontal health, especially considering the escalating emphasis on the connection between periodontal health and overall health."
Male participants aged 49 through 59 were examined on three indicators of periodontal disease: periodontal pocket depth (PD), clinical attachment loss (CAL) of gum tissue, and bleeding on probing (BOP) of the gum tissue. Researchers observed that for every one cup of green tea consumed per day, there was a decrease in all three indicators, therefore signifying a lower instance of periodontal disease in those subjects who regularly drank green tea.
Green tea's ability to help reduce symptoms of periodontal disease may be due to the presence of the antioxidant catechin. Previous research has demonstrated antioxidants' ability to reduce inflammation in the body, and the indicators of periodontal disease measured in this study, PD, CAL and BOP, suggest the existence of an inflammatory response to periodontal bacteria in the mouth. By interfering with the body's inflammatory response to periodontal bacteria, green tea may actually help promote periodontal health, and ward off further disease. Periodontal disease is a chronic inflammatory disease that affects the gums and bone supporting the teeth, and has been associated with the progression of other diseases such as cardiovascular disease and diabetes.
"Periodontists believe that maintaining healthy gums is absolutely critical to maintaining a healthy body," says Dr. David Cochran, DDS, PhD, President of the AAP and Chair of the Department of Periodontics at the University of Texas Health Science Center at San Antonio. "That is why it is so important to find simple ways to boost periodontal health, such as regularly drinking green tea – something already known to possess certain health-related benefits."
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Minggu, 08 Maret 2009

Bioteknologi Tanaman

Dewasa ini, teknik-teknik bioteknologi tanaman telah dimanfaatkan terutama untuk memberikan karakter baru pada berbagai jenis tanaman. Penekanan pemberian karakter tersebut dapat dibagi kedalam beberapa tujuan utama yaitu peningkatan hasil, kandungan nutrisi, kelestarian lingkungan, dan nilai tambah tanaman-tanaman tertentu. Sebagai contoh, beberapa tanaman transgenik yang dikembangkan adalah:

  1. Peningkatan kandungan nutrisi: Pisang, cabe, raspberries, stroberi, ubi jalar
  2. Peningkatan rasa: tomat dengan pelunakan yang lebih lama, cabe, buncis, kedelai
  3. Peningkatan kualitas: pisang, cabe, stroberi dengan tingkat kesegaran dan tekstur yang meningkat
  4. Mengurangi alergen: polong-polongan dengan kandungan protein allergenik yang lebih rendah
  5. Kandungan bahan berkhasiat obat: tomat dengan kandungan lycopene yang tinggi (antioksidan untuk mengurangi kanker), bawang dengan kandungan allicin untuk menurunkan kolesterol, padi dengan kandungan vitamin A dan besi untuk mengatasi anemia dan kebutaan,
  6. Tanaman untuk produksi vaksin dan obat-obatan untuk mengobati penyakit manusia
  7. Tanaman dengan kandungan nutrisi yang lebih baik untuk pakan ternak
    dan lain-lain .

Selain itu, pemanfaatan bioteknologi tanaman seperti rekayasa genetika juga dapat memudahkan petani dalam budidaya tanaman. Misalkan dalam pengendalian gulma yaitu dengan menghasilkan tanaman yang memiliki ketahanan terhadap jenis herbisida tertentu. Sebagai contoh adalah Roundup Ready yang terdiri dari kedelai, canola dan jagung yang tahan terhadap herbisida Roundup. Di dunia saat ini telah banyak dilepas berbagai tanaman transgenik. Sebagai contoh, di Asia yaitu di China pada tahun 2006 saja, telah telah ada sekitar 30 spesies tanaman transgenik, antara lain padi, jagung, kapas, rapeseed, kentang, kedelai, poplar, tomat (delay ripening dan ketahanan virus), petunia (warna bunga), paprika (virus resistance), kapas (ketahanan hama) yang telah dilepas untuk produksi.

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Kemajuan dan penerapan bioteknologi tanaman pada tanaman pangan

Kemajuan dan penerapan bioteknologi tanaman tidak terlepas dari tanaman pangan. Untuk memenuhi kebutuhan pangan dunia termasuk kebutuhan nutrisi, kemajuan bioteknologi telah mewarnai trend produksi pangan dunia. Padi saat ini masih merupakan tanaman pangan utama dunia. Dengan demikian prioritas utama untuk teknik biologi molekuler dan transgenik saat ini masih diutamakan pada padi. Selain karena merupakan tanaman pangan utama, padi memiliki genom dengan ukuran sehingga dapat digunakan sebagai tanaman model utama. Selain padi tanaman pangan yang telah banyak mendapat sentuhan bioteknologi adalah kentang.
Golden Rice

Penerapan bioteknologi pada tanaman padi sebenarnya telah lama dilakukan namun menjadi sangat terdengar ketika muncul golden rice pada tahun 2001 yang diharapkan dapat membantu jutaan orang yang mengalami kebutaan dan kematian dikarenakan kekurangan vitamin A dan besi. Vitamin A sangat penting untuk penglihatan, respon kekebalan, perbaikan sel, pertumbuhan tulang, reproduksi, hingga penting untuk pertumbuhan embrionik dan regulasi gen-gen pendewasaan.
Luasan lahan pertanian yang semakin sempit mengakibatkan produksi perlahan harus ditingkatkan. Peningkatan ini tidak hanya berupa peningkatan bobot panen namun juga nutrisi atau nilai tambah. Oleh sebab itu dari suatu luasan yang sebelumnya hanya menghasilkan karbohidrat diharapkan dapat ditambah dengan vitamin dan mineral. Hal inilah yang mendorong para peneliti padi mengembangkan Golden Rice. Pada awalnya penelitian dilakukan untuk meningkatkan kandungan provitamin A berupa beta karoten, dan saat ini fokus penelitian tetap dilakukan.
Nama Golden Rice diberikan karena butiran yang dihasilkan berwarna kuning menyerupai emas. Rekayasa genetika merupakan metode yang digunakan untuk produksi Golden Rice. Hal ini disebabkan karena tidak ada plasma nutfah padi yang mampu untuk mensintesis karotenoid. Pendekatan transgenik dapat dilakukan karena adanya perkembangan teknologi transformasi dengan Agrobacterium dan ketersediaan informasi molekuler biosintesis karotenoid yang lengkap pada bakteri dan tanaman. Dengan adanya informasi tersebut terdapat berbagai pilihan cDNA. Produksi prototype Golden Rice menggunakan galur padi japonica (Taipe 309), teknik transformasi menggunakan agrobacterium dan beberapa gen penghasil beta karoten tanaman daffodil hingga bakteri.
Bioteknologi Tanaman Kentang

Tanaman pangan dunia yang tidak kalah penting adalah kentang. Seperti halnya padi, kentang juga menjadi komoditas utama yang menjadi obyek penerapan bioteknologi tanaman. Teknik bioteknologi saat ini telah banyak digunakan dalam produksi kentang. Baik dalam teknik penyediaan bibit, pemuliaan kentang, hingga rekayasa genetika untuk meningkatkan sifat-sifat unggul kentang. Dalam hal penyediaan bibit, saat ini teknik kultur jaringan telah banyak digunakan. Teknik kultur jaringan memungkinkan petani mendapatkan bibit dalam jumlah besar yang identik dengan induknya.
Teknik kultur jaringan juga dapat digunakan untuk menghasilkan umbi mikro (microtuber). Produksi kentang dari umbi mikro dan umbi konvensional menurut penelitian tidak berbeda nyata. Gambar 2. Skema produksi bibit kentang melalui teknik kultur jaringan. Umbi mikro kentang Selain itu teknik kultur jaringan pada tanaman kentang juga bermanfaat terutama untuk preservasi in vitro, fusi protoplas dan membantu dalam seleksi pada skema pemuliaan tanaman. Pemuliaan kentang dilakukan untuk meningkatkan sifat-sifat unggul dan menambah sifat baru sesuai kondisi yang diharapkan. Salah satu kendala utama produksi kentang adalah serangan penyakit yang tinggi sehingga pemuliaan kentang sering diarahkan untuk meningkatkan tingkat ketahanan tanaman terhadap penyakit. Jika dilakukan secara konvensional diperlukan sedikitnya 15 tahun untuk menghasilkan kultivar baru. Hal ini terjadi karena kentang komersial pada umumnya adalah tetraploid sehingga persilangan kentang akan menghasilkan keragaman yang sangat tinggi. Untuk mengatasi permasalahan ini teknik seleksi awal dengan teknik in vitro telah dilakukan serta dapat juga dilakukan melalui marker assisted breeding (MAS). Untuk meningkatkan sifat ketahanan dan sifat lain pendekatan rekayasa genetika juga telah dilakukan melalui fusi protoplast dan tranformasi genetik.
Contoh pemanfaatan teknik transformasi agrobacterium pada tanaman kentang adalah dengan menyisipkan gen dari spesies liar yaitu Rpi-blb, Rpi-blb2 yang dapat meningkatkan ketahanan terhadap Phytopthora infestans. Kentang tersebut dinamakan dengan kultivar Kathadin. Contoh lain adalah kentang dengan kandungan pati yang tinggi yang dapat menghasilkan kentang goreng dan kripik kentang dengan kualitas yang lebih baik karena menyerap lebih sedikit minyak ketika digoreng. Kentang ini dirakit dengan rekayasa genetika dengan menginsert gen dari bakteri ke kentang Russet Burbank. Gen tersebut dapat meningkatkan kandungan pati umbi yang dihasilkan dan menurunkan penyerapan minyak sewaktu digoreng. Hal ini dianggap menguntungkan karena dapat menurunkan biaya produksi sekaligus lebih sehat bagi konsumen. Uji lapangan kultivar Katahdin terhadap serangan Phytopthora infestans. Tampak Kathadin lebih tahan dibandingkan dengan kentang kontrol
Kemajuan dan penerapan bioteknologi tanaman pada tanaman hortikultura

Dengan semakin meningkatnya pendapatan dan kesadaran masyarakat akan arti penting kesehatan, kebutuhan akan produk-produk hortikultura sebagai sumber vitamin meningkat. Selain itu dari sisi kesehatan mental, kebutuhan produk hortikultura yang lain yaitu berbagai tanaman hias turut meningkat. Teknik kultur jaringan telah dimanfaatkan secara luas pada tahaman hortikultura, seperti perbanyakan klonal yang dikombinasikan dengan teknik bebas virus pada kentang, pisang, anggur, apel, pear dan berbagai jenis tanaman hias, serta penyelamatan embrio untuk mendapatkan tanaman hibrida dari hasil persilangan interspecies. Teknologi rekayasa genetika juga telah diaplikasikan pada tanaman hortiklutura. Sebagai contoh yang cukup terkenal adalah Tomat FlavrSavr. Tomat merupakan salah satu produk hortikultura utama. Seperti produk hortikultura pada umumnya, tomat memiliki shelf-life yang pendek.
Shelf-life yang pendek ini disebabkan dengan aktifnya beberapa gen seperti pectinase saat tomat mengalami kematangan. Dengan kondisi seperti ini, tomat sulit sekali untuk dipasarkan ke tempat yang jauh terlebih untuk ekspor. Biaya pengemasan sangat mahal seperti menyediakan box yang dilengkapi pendingin. Untuk mengatasi hal ini para peneliti di Amerika mencoba merekayasa kerja gen polygalacturonase (PG) yang berasosiasi dengan shelf-life tomat yaitu dengan menginsert antisense dari gen PG.
Dengan demikian shelf-life tomat menjadi lebih lama. Tomat ini dinamakan dengan FlavrSavr. Pada industri tanaman hias, teknik kultur jaringan telah digunakan secara meluas pada berbagai tanaman hias. Teknik kultur jaringan yang diaplikasikan mencakup kultur meristem, organogenesis dan somatic embryogenesis, konservasi, eliminasi patogen.
Sementara itu untuk meningkatkan keragaman dapat memanfaatkan adanya variasi somaklonal. Hal ini sangat penting dilakukan mengingat tanaman hias kebanyakan dinilai dari segi estetika dan kelangkaannya, serta bentuk-bentuk baru seperti bentuk serta warna daun dan bunga, arsitektur tanaman, serta sifat-sifat unik tanaman tertentu. Teknik lain untuk keperluan ini adalah mutasi. Pada industri tanaman hias dalam pot sering digunakan Zat Pengatur Tumbuh untuk mengatur pola pertumbuhan dan perkembangan tanaman. Contohnya adalah penggunaan retardan untuk membuat pertumbuhan menjadi pendek dan meroset.
Pemanfaatan rekayasa genetika pada tanaman hias berpotensi untuk menambahkan sifat-sifat baru yang unik. Contoh tanaman yang telah direkayasa antara lain krisan dan mawar dengan tingkat ketahanan dan vase life yang lebih tinggi.
Kemajuan dan penerapan bioteknologi tanaman pada tanaman perkebunan

Bioteknologi juga diterapkan pada beberapa tanaman perkebunan seperti tebu, tembakau, kelapa sawit dan lain-lain. Hingga saat ini kapas merpuakan komoditas yang paling banyak mendapat sentuhan bioteknologi. Di Amerika, hingga saat ini tanaman transgenik yang paling banyak dilepas adalah kapas.
Kapas transgenik yang terkenal adalah kapas Bt (Bacillus thuringiensis). Dengan introduksi gen Bt ke tanaman kapas, tanaman kapas menjadi tahan terhadap hama yang disebabkan tanaman dapat memproduksi protein Bt-toxin. Bt pertama ditemukan tahun 1911 dan terdaftar sebagai biopestisida di Amerika Serikat tahun 1961.
Salah satu dari sekian banyak kerugian merokok adalah gangguan kesehatan karena kadar nikotin yang tinggi. Pendekatan bioteknologi dilakukan untuk mengatasi permasalahan ini yaitu dengan merakit tanaman tembakau yang bebas kandungan nikotin. Dengan cara ini perokok dapat terkurangi resiko gangguan kesehatannya.
Pada tahun 2001 jenis tembakau ini diklaim dapat mengurangi resiko serangan kanker akibat merokok. Selain bebas nikotin, sentuhan bioteknologi lain juga dilakukan untuk tanaman tembakau misalnya dengan meningkatkan aroma menggunakan gen aroma dari tanaman lain. Salah satu yang telah berhasil adalah menggunakan monoterpene synthase dari lemon.
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Defense Mechanisms

Defense mechanisms are very important to all animal life. Animals must eat to survive. With predators always on the lookout for a meal, prey must constantly avoid being eaten. Any adaptation the prey uses adds to the chances of survival for the species. Some adaptations are defense mechanisms which can give the prey an advantage against enemies.

Leopard camouflaged in the grass.U.S. Fish and Wildlife Service/Gary Stolz



Defense Mechanisms


There are several ways animals avoid falling prey to a predator. One way is very direct and comes naturally. Imagine you are a rabbit and you have just noticed a fox preparing to attack. What would be your initial response? Right, you'd run. Animals can use speed as a very effective means of escaping predators. Remember, you can't eat what you can't catch!

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Another defense mechanism is camouflage or protective coloration. One form, cryptic coloration, allows the animal to blend in with its environment to avoid being detected. It is important to note that predators also use cryptic coloration to avoid detection by unsuspecting prey.


Trickery can also be used as a formidable defense. False features that appear to be enormous eyes or appendages can serve to dissuade potential predators. Mimicking an animal that is dangerous to a predator is another effective means of avoiding being eaten.


Physical or chemical combat are other types of defense mechanisms. Some animals' physical features make them a very undesirable meal. Porcupines, for example, make it very difficult for predators with their extremely sharp quills. Similarly, predators would have a tough time trying to get to a turtle through its protective shell.


Chemical features can be just as effective. We all know the hazards of scaring a skunk! The chemicals released result in a not so pleasant aroma that an attacker will never forget. The dart frog also uses chemicals (poisons secreted from its skin) to deter attackers. Any animals that eat these small frogs are likely to get very sick or die.

Predator-Prey Relationship


To sum it all up, the predator-prey relationship is important to maintaining balance among different animal species. Adaptations that are beneficial to prey, such as chemical and physical defenses, ensure that the species will survive. At the same time, predators must undergo certain adaptive changes to make finding and capturing prey less difficult.


Without predators, certain species of prey would drive other species to extinction through competition. Without prey, there would be no predators. Thus, this relationship is vital to the existence of life as we know it.
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Trust Your Heart: Emotions May Be More Reliable When Making Choices

When choosing a flavor of ice cream, an item of clothing, or even a home, you might be better off letting your emotions guide you, according to a new study in the Journal of Consumer Research.


"Our current research supports theories in evolutionary psychology that propose that our emotions can be conceived as a set of 'programs' that have evolved over time to help us solve important recurrent problems with speed and accuracy, whether it is to fall in love or to escape from a predator," write authors Leonard Lee (Columbia Business School), On Amir (University of California, San Diego), and Dan Ariely (Duke University).
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"We investigated the following question: To what extent does relying on one's feelings versus deliberative thinking affect the consistency of one's preferences?" write the authors. To get at the question, the authors designed experiments where participants studied and chose among 8-10 products, sometimes relying upon their emotional reactions and sometimes calling upon cognitive skills. Their conclusion: "Emotional processing leads to greater preference consistency than cognitive processing."
The researchers made some additional discoveries about eliciting consistent choices from participants. The study participants tended to make more consistent choices when products were represented by pictures instead of names; when pictures were in color (rather than black and white); when participants were encouraged to trust their feelings when making their choices; when the participants had greater cognitive constraints (i.e., when they were asked to memorize a ten-digit number as opposed to a two-digit one); and when the products tended to be more exciting (a pen with a built-in FM radio receiver) rather than functional (an LED book light).
It seems the old adage "trust your heart" is true for consumers. "If one buys a house and relies on very cognitive attributes such as resale value, one may not be as happy actually purchasing it," write the authors. "Indeed, our results suggest that the heart can very well serve as a more reliable compass to greater long-term happiness than pure reason."
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How We Make Decisions


The frontal lobe is a region of the cerebral cortex of the brain that is responsible for decision-making, problem solving, and planning. Researchers have now discovered the specific areas of the frontal lobe that control abstract and concrete decision-making. The front portion of the frontal lobe handles abstract decisions and the back portion handles concrete decisions.
Photo credit: Gray's Anatomy

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For example, if you had an idea that you wanted to bake some cookies, the decision process would start at the front portion of the frontal lobe. As you begin to determine the actions involved in making the cookies, a more concrete decision, the back portion of the frontal lobe would be involved. Understanding exactly how this part of the brain works could be very important to finding new treatments for strokes and other brain disorders.

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Bacterial Reproduction

Bacteria are prokaryotic organisms that reproduce asexually. Bacterial reproduction most commonly occurs by a kind of cell division called binary fission. Binary fission results in the formation of two bacterial cells that are genetically identical.
Bacterial Cell Structure
Bacterial cells typically contain the following structures: a cell wall, cell membrane, cytoplasm, ribosomes, plasmids, flagella, and a nucleiod region.
  • Cell Wall - Outer covering of the cell that protects the bacterial cell and gives it shape.
  • Cytoplasm - A gel-like substance composed mainly of water that also contains enzymes, salts, cell components, and various organic molecules.
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  • Cell Membrane or Plasma Membrane - Surrounds the cell's cytoplasm and regulates the flow of substances in and out of the cell.
  • Flagella - Long, whip-like protrusion that aids in cellular locomotion.
  • Ribosomes - Cell structures responsible for protein production.
  • Plasmids - Gene carrying, circular DNA structures that are not involved in reproduction.
  • Nucleiod Region - Area of the cytoplasm that contains the single bacterial DNA molecule.

Bacterial Reproduction:

AsexualMost bacteria reproduce by binary fission. During binary fission, the single DNA molecule replicates and both copies attach to the cell membrane.The cell membrane begins to grow between the two DNA molecules. Once the bacterium just about doubles its original size, the cell membrane begins to pinch inward.A cell wall then forms between the two DNA molecules dividing the original cell into two identical daughter cells.

Bacterial Recombination:

Binary fission is an effective way for bacteria to reproduce, however it does produce problems. Since the cells produced through this type of reproduction are identical, they are all susceptible to the same types of antibiotics. In order to incorporate some genetic variation, bacteria use a process called recombination. Bacterial recombination can be accomplished through conjugation, transformation, or transduction.

Conjugation

Some bacteria are capable of transferring pieces of their genes to other bacteria that they come in contact with. During conjugation, one bacterium connects itself to another through a protein tube structure called a pilus. Genes are transferred from one bacterium to the other through this tube.

Transformation

Some bacteria are capable of taking up DNA from their environment. These DNA remnants most commonly come from dead bacterial cells. During transformation, the bacterium binds the DNA and transports it across the bacterial cell membrane. The new DNA is then incorporated into the bacterial cell's DNA.

Transduction

Transduction is a type of recombination that involves the exchanging of bacterial DNA through bacteriophages. Bacteriophages are viruses that infect bacteria. There are two types of transduction: generalized and specialized transduction.Once a bacteriophage attaches to a bacterium, it inserts its genome into the bacterium. The viral genome, enzymes, and viral components are then replicated and assembled within the host bacterium. The newly formed bacteriophages then lyse or split open the bacterium, releasing the replicated viruses.During the assembling process however, some of the host's bacterial DNA may become encased in the viral capsid instead of the viral genome. When this bacteriophage infects another bacterium, it injects the DNA fragment from the previous bacterium. This DNA fragment then becomes inserted into the DNA of the new bacterium. This type of transduction is called generalized transduction.In specialized transduction, fragments of the host bacterium's DNA become incorporated into the viral genomes of the new bacteriophages. The DNA fragments can then be transfered to any new bacteria that these bacteriophages infect.
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