Why do some scientist believe that RNA, rather than DNA, was the first genetic material
|
Displaying 241 - 245 of 1057 questions. Show How RNA is progenator of life? Asked by: Rakesh Bandol
Latest Reply: Hello Rakeshb, Scientists have hypothesized that RNA played a key role in the origins of life. In 1986, Walter Gilbert hypothesized that there was once an “RNA world.” During this hypothetical period, RNA served as the genetic material and it also performed all the enzymatic activities necessary to replicate itself in early life forms. The RNA world hypothesis is based on the observation that RNA is able to perform two key tasks essential for life: 1) it can store genetic information, and 2) it can catalyze chemical reactions. As part of this view, as life evolved further, DNA became the genetic storage material in cells in place of RNA, and proteins replaced RNA as the main catalysts of the chemical reactions in cells. According to this hypothesis, cells still carry remnants of the RNA world. For example, the ribosome is an intermediate structure made up of both RNA and proteins, in which RNA catalyzes the synthesis of proteins. So, why did DNA evolve to be the primary genetic material over RNA? According to the RNA world hypothesis, DNA evolved to store the genetic information instead of RNA because DNA is chemically more stable than RNA. Moreover, since DNA has a double-stranded structure, it has the ability to correct errors in replication. Scientists are currently researching RNA molecules to better understand their many functions and to support or refute the hypothesis that an RNA world once existed. Intriguingly, some scientists believe that a pre-RNA world existed before the RNA world and that even more simple molecules existed before RNA. Here are a few links to learn more about the RNA world and the pre-RNA world hypotheses. Happy reading! To learn more about the “RNA world” and the various functions of RNA, check out the following
links: Reply From: Nature Education May 20, 2013 08:22PM small mutation can occur in our body even at normal conditions(eg,at 40degrees in a room), then why do we remain unaffected by that type of small mutations ??? Asked by: abhijay pareek
Latest Reply: Dear Abhijay, This is an excellent question, and one that has taken researchers decades to answer. In short, our cells contain a number of different types of proteins that all work together to detect and fix all sorts of mutations, including those that accumulate through the normal process of cell division. These types of errors are called replication errors, and they occur when the enzyme that makes new DNA — DNA polymerase — makes a mistake and doesn’t catch it. Replication errors come in three forms: 1) mismatches, 2) improper nucleotide insertions, and 3) improper nucleotide deletions. Mismatches occur when DNA polymerase inserts the wrong nucleotide, and the DNA has to bend or become distorted to accommodate the resulting non-natural base pairing. Improper nucleotide insertions or deletions can occur when DNA polymerase incorrectly skips a base or inserts an extra copy of a base. When this happens, the DNA structure forms a sort of bubble, where the two ends are tethered together by correctly grouped nucleotides and the bubble is centered over the error. In the case of a nucleotide insertion, the bubble forms in the newly replicated DNA. In the case of a nucleotide deletion, the bubble forms in the old, parental DNA strand. Fortunately, our cells possess back-up repair processes that step in when the DNA polymerase has made a mistake and moved on. As a whole, proteins called “DNA repair proteins” facilitate these processes, and they can be grouped according to the type of mutation they fix and how they operate. For instance, mismatch repair proteins are so named because they recognize and repair mismatched DNA. These DNA repair mechanisms are continuously working to find and correct new DNA mutations. It is for this reason that the estimated thousands of mutations that arise each time our cells divide do not affect us. There are in fact thousands of articles (and even an entire scientific journal, called DNA Repair) describing the DNA repair proteins and how they interact in all sorts of situations. We hope the information we’ve provided has helped answer your question and fueled your curiosity about how amazing our cells are! Check out these links to some of our favorite articles about the DNA repair processes we’ve discussed:
Reply From: Nature Education May 20, 2013 08:18PM Your friend knows that you took Human Biology and studied genetics. She asks you to explain a Punnett square to her. How do you explain how a Punnett square is read? Apply the following terms to your explanation: dominant, recessive, one-trait & two-trait crosses, Dihybrid cross and probability. Asked by: mandy mccune
Latest Reply: Hello Mandy, A Punnett square is a grid that is used to view the potential combinations of parental alleles in the offspring of a genetic cross. You’re in luck, because there’s a concept page here at Scitable with a step-by-step explanation of how to draw and read Punnett squares for monohybrid and dihybrid crosses. This page also includes definitions of the terms you’ve listed above. Good luck with your Human Biology studies! Reply From: Nature Education May 20, 2013 08:12PM what are the effects of pressure in plants? Asked by: KRISHNA S.NAIR
Latest Reply: Hello Krishna, Your question about how pressure affects plants is very interesting. Even though it may sound like science fiction, there is interest about what happens to plants in lower atmospheric pressure because scientists wonder whether plants could grow well in a spacecraft or even on other planets, such as Mars! It turns out that even though there are changes in gene expression for plants under low atmospheric pressure, plants do surprisingly well under these conditions. If oxygen levels are kept constant, then mung bean and lettuce seedlings grow just as well and may even get slightly larger than normal under low atmospheric pressure conditions! It will be interesting to see how space programs use this information in the future. If you’d like to learn more the effect(s) of low atmospheric pressure on plants, check out the following
links: Reply From: Nature Education May 20, 2013 08:08PM Profesor quién es Mendel Asked by: Claudia Pleguezuelos
Latest Reply: Dear Claudia, Considered to be the “father of modern genetics,” Gregor Mendel was an Augustinian monk who lived in what is now the Czech Republic. Between 1856 and 1863, he experimented with crossbreeding pea plants to establish many of the rules of heredity. Mendel performed crossbreeding experiments over several generations and looked at seven traits in the parent and offspring plants, including seed shape and color. Through his research, he noticed that certain traits were dominant to others, and he coined the terms “dominant” and “recessive.” For example, he found that yellow (dominant form) pea plants crossbred with green (recessive form) pea plants always yielded yellow pea plants. In the next generation, green pea plants reappeared at a ratio of 1 green to 3 yellow. Other scientists had noticed the disappearance and reappearance of traits in plants, but Mendel carefully kept track of the phenotypes of parents and offspring in different breeding configurations, and did so on a large scale. He pollinated flowers of around 28,000 plants on two acres of his monastery gardens. Mendel published his findings in his paper “Experiments on Plant Hybridization” in 1866, but the significance of his work was not recognized before he passed away in 1884. Three scientists rediscovered Mendel’s paper in 1900, and the value of his contributions to the then new field were realized. For more information about Mendel and the principles of inheritance, check out these
links: Visit this link to read Mendel’s paper “Experiments on Plant Hybridization”: For information about the Mendel Museum in the Czech Republic, see this link: Reply From: Nature Education May 20, 2013 08:05PM 
Send MessageWhy is RNA considered as the first genetic material?According to this hypothesis, RNA stored both genetic information and catalyzed the chemical reactions in primitive cells. Only later in evolutionary time did DNA take over as the genetic material and proteins become the major catalyst and structural component of cells.
Why could DNA not be the first genetic material?RNA has great capability as a genetic molecule; it once had to carry on hereditary processes on its own. It now seems certain that RNA was the first molecule of heredity, so it evolved all the essential methods for storing and expressing genetic information before DNA came onto the scene.
Which do scientists believe evolved first RNA or DNA?It can drive chemical reactions, like proteins, and carries genetic information, like DNA. And because RNA can do both these jobs, most scientists think life as we know it began in an RNA world, without DNA and proteins.
Why do scientists think that RNA might have been the first catalyst?RNA seemed a likely first biomolecule, because, like DNA, it can store information, and, like proteins, it can act as a catalyst to speed up certain chemical reactions. Researchers also discovered early on that RNA is at the core of several modern enzymes critical to life, such as the ribosome that builds proteins.
|
