→ GAG (glutamic acid) GAG First →GTG Exact (glutamic acid) mutation (valine) reversion First →GTG Equivalent (glutamic acid) mutation (valine) reversion GAG > GAA (glutamic acid) Equivalent > GAT (aspartic acid) GAG First →GTG (glutamic acid) mutation (valine) reversion
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
A reversion is a mutation that returns a mutant codon back to a
codon that gives a wild-type
of mutation can be an exact reversion or an equivalent reversion.
An equivalent reversion produces a protein that is equivalent to the
wild-type protein in structure and function. This outcome can
occur in two ways. In some cases, the reversion produces the
wild-type amino acid (in this case, glutamic acid), but it uses a
different codon than the wild-type gene. Alternatively, an equivalent
reversion may substitute an amino acid structurally similar
to the wild-type amino acid. In our example, an equivalent reversion
has changed valine to an aspartic acid. Because aspartic and
glutamic acids are structurally similar—they are acidic amino
acids—this type of reversion can restore wild-type structure and
function.
Here is the question: The template strand within the coding
sequence of a gene has the following sequence:
3′–TACCCCTTCGACCCCGGA–5′
This template produces the following mRNA:
5′–AUGGGGAAGCUGGGGCCA–3′
The mRNA encodes a polypeptide with the following sequence:
methionine–glycine–lysine–leucine–glycine–proline
A mutation changes the template strand to this sequence:
3′–TACCCCTACGACCCCGGA–5′
After the first mutation, another mutation occurs to change this
sequence again. Is each of the following second mutations an exact
reversion, an equivalent reversion, or neither?
A. 3′–TACCCCTCCGACCCCGGA–5′
B. 3′–TACCCCTTGACCCCGGA–5′
C. 3′–TACCCCGACGACCCCGGA–5′
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