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.
As we learned when studying protein trafficking, proteins need a nuclear localization signal in order to move from the cytosol into the nucleus via the nuclear pore complex. Protein A contains a typical nuclear localization signal but surprisingly is usually found in the cytosol. When the cell is exposed to a certain hormone, protein A moves from the cytosol
into the nucleus, where it turns on genes involved in cell division.
When you purify protein A from cells that have not been treated with the hormone, you find that protein B is always complexed with it. To determine the function of protein B, you engineer cells lacking the gene for protein B. You compare normal and gene B deletion cells by separating and isolating the proteins found in the cytoplasm and those found in the nucleus. You then run these proteins on a protein electrophoresis gel to separate them
by size. You identify the presence of protein A and protein B by looking for their characteristic bands on the gel (which is shown in the attached image).
a) Based on these results, what is the function of protein B? Briefly explain your
reasoning.
b) Please propose a plausible mechanism for how protein B might work
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