1. How would redundancy in the gentic code influence whether a mutation in DNA w
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Question
1. How would redundancy in the gentic code influence whether a mutation in DNA would have an effect or not?
2.In the real world, what determines if a change in genetic make-up is "good", "bad", or "has no effect"?
3. Mutation is the source of new genetic information and the environment "decides" its value. Acting together, how do these dynamic force shlep to explain biodiversity (i.e. why are there so many different kinds of organisms)?
4. Since all species use the same genetic code, one type of organism can express the genes of another if it becomes part of its genome. This is the basis of genetic engineering, whereby DNA sequences (genes of one species) are inserted into the cells of another. Would an "engineered" organism be considered a mutation or a new speices? Justify your answer
5. DNA profiling has many beneficial uses. However, what are two possible drawbacks to widepsread profiling?
Explanation / Answer
1 Redudancy in genetic code means that a single amino acid can be coded by many different codons. For example leucine can be coded by CUU, CUC,CUA, CUG. If there is a point mutation in the codon i.e if CUU is mutated to CUC it will still code for the same amino acid leucine.
2 If mutation in codons lead to incorporation of completely different amino acid then that's a bad effect. For example if GAG coding for glutamate undergoes point mutation to GUG coding for valine, then nature of amino acid is completely changed. Glutamate is a negatively charge polar amino acid , whereas valine is a hydrophobic amino acid. This transition can completely hamper the folding of a protein to achieve its native state. This happens in sickle cell anemia. Replacement of glutamate by valine in the beta chain of hemoglobin produces a sticky hydrophobic spot on the surface that results in abnormal association of hemoglobin subunits. This makes abnormal deoxy hemoglobin less soluble than normal deoxy hemoglobin . These insoluble deoxy hemoglobin aggregate into tubular fibers and distort RBC into elongated sickle structure.
certain mutations in codons can produce stop codon leading to truncated proteins. Example UGG coding for tryptophan can be mutated to UGA which is a stop codon.
3. Mutations leads to variations and any beneficial variation which gives survival benefit/ advantage to an individual becomes naturally selected. Darwin said that individuals having advantageous variations are more likely to survive and reproduce than those without the advantageous variation. Classic example is the neck of giraffe. During food scarcity longer necked individuals survived because they are able to exploit food unavailable to short necked individuals. Therefore long- necked giraffe perpetuated and survived in greater numbers.
Darwin also said that variations exist among individual species and that species have a common descent. Through changes in genetics they have undergone speciation. These changes can be related to the surroundings. Example is the galapagos islands and darwins finches. galapagos finches (group of 14 species of small birds, 13 occur in galapagos) descended from a common ancestral species. These birds would occassionally migrate to new islands and inhabit them. On these new island they would become adjusted to local conditions of food and weather through natural selection. descendants of the original finches now occupy different habitats. In this process they became progressively more different from original populations. The most visible difference is related to dietry adaptations and is reflected in the size and shape of their beaks.
Genetics are also modified by environmental influences. This is also known as epigenetics. Certain environmental stimuli can have direct effect on the genome leading to switching on or off of susceptible genes. Such changes can pass on to next generation creating variation in individuals.
4. An engineered species where a particular gene is inserted into the genome from a different source is called transgenic organism. Example : Bt cotton is a transgenic plant. It has a microbial protein gene which codes for a endotoxin, inserted into its genome. This endotoxin helps the transgenic plant to kill insects.
This whole process of transferring genesinto a organism is called transgenesis
Engineered organism cannot be called a new species as the addition of a new gene is for creation of a better plant variety. Simliarly, recombinant clones of microbes are created for large scale insulin production by inserting insulin gene into the bacterial genome
It can also not be called a mutation. Mutation causes deleterious effect by impairing gene sequence and its function. However, In case of Genetically modified organisms, a functional gene is created. Mutation is not known to insert gene into new places, even if it does, ( in case of translocation) it causes production of an abnormal product.
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