Question

1) What is the molecular basis of dominant and recessive alleles (for complete dominance; ignore incomplete dominance, epistasis, etc.)? To answer this question, consider the following:

a) If alleles are copies of the same gene, why are two types of alleles? What differentiates a dominant allele from a recessive allele (at the molecular level)? Be specific (base pairs, transcription/translation method, protein produced, etc.)

b) Why is the phenotype determined by the dominant allele in heterozygous genotype? Be specific.

c) What role does mutation play in recessive genetic diseases (heterozygous and homozygous recessive genotypes)? Refer to protein production. How is the mutation silenced in the heterozygous genotype?

d) What role does mutation play in dominant genetic diseases? If the dominant allele suppresses the expression of a recessive allele, how would a mutation of the dominant allele affect the phenotype? Would the mutated dominant allele still suppress the expression of the non-mutated recessive allele? How?

Answer 1

The answer to all these questions lie on the simple concept that

A dominant allele is the one which can code for a protein and hence the physical appearance of character occurs whereas its counterpart (slightly changed form )located on the same location at the homologous chromosome does not produce a functional rna and does not code for any protein hence it is not expressed .Now we know in genetics there is nothing such as produce /not produce ,on/off BUT off /not produce simply refer to the fact that the quantity is low rather than being completely nil .Hope u got all your answers :)