1. Consider a mutation involving the deletion of either 1, 2, or 3 nucleotides i
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Question
1. Consider a mutation involving the deletion of either 1, 2, or 3 nucleotides in the DNA of a bacterium. Which of these mutations (i.e., deletion of 1, 2, or 3 nucleotides) would likely have the LEAST impact on the organism? Why? Include in your answer a comparison with the other two options to justify your reasoning. Think carefully about the impact each mutation would have on the ultimate protein coded for by the gene.
2. Spontaneous mutations of a single nucleotide, or point mutations, result from the incorporation of an incorrect nucleotide during DNA replication. Although these point mutations represent a change of the genotype of the organism, in some cases they may not change the phenotype. Please explain how this is possible.
3. Explain the process of gene expression. Include the components involved up through the final product.
4. Consider all the E. coli bacteria of a particular strain and assume they all arose from a common ancestor and possess the exact same DNA in their chromosome. (Note that this is unlikely to really be true!) Explain why they could all have exactly the same DNA, but their RNA would likely vary widely from one cell in one location to another cell in another location.
Explanation / Answer
1.
Mutation results in change in genetic makeup either by inserting or deleting one or more nucleotide. In cells genetic code is used to translate language of nucleic acids into amino acids.
If a mutation results in loss of one or two nucleotide results in more severe effect on genetic translation as compared to addition or deletion of three nucleotide. Reason being a genetic code is made up of three nucleotides and thus mutation with nucleotide results in removal of a codon thus eliminating a complete amino acid code. Since the code is degenerate (more than one codon per amino acid, in most cases) loss of coding of an amino acid in case of frame shift mutation where three nucleotides are deleted or added can be compensated by some other codon.
2. Few mutations do not affect the phenotype of the organism. This can be explained on two bases, first either the mutation has happened in stretch of DNA which do not code for any function and thus mutation has not affect. Seconds could be although mutation has affected the protein coding region but it does not affect translation in the code.
3.
The process which directs the protein synthesis through genetic code and nucleotide sequence is termed as Gene Expression. Genes which code for amino acid sequence are termed as “Structural Genes”.
The process of Gene Expression involves two main stages:
4. DNA is used to produce mRNA byt he process termd as transcription. mRNA produced from this process is further used to produce protein. As each mRNA is specific for a specific protein, it varies in different species of E.Coli bacteria which has similar DNA. As protein requirement also depends on physical condition mRNA produced will be protein specific resulting in differences in RNA.
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