Question

is genomic or mRNA sequence more useful for drawing a conclusion regarding homology? why?

Answer 1

Homology basically means organs that have different functions but are from a similar embryonic origin and development i.e., common ancestor. It indicates relationships between their possessors. Example, proteins present in blood of man and ape are similar. mRNA sequences can be used s guideline for drawing conclusion regarding homology. The reason being the problems with DNA:

• Codon Bias: This explains that not all codons for a particular protein re used in the genes of a particular organism. Example, for any given protein there might be multiple codons.
• Upstream regulatory sequences: they have distinct sequence features that act as recognition signals, but these are variable.
• Extron intron boundaries: have distinctiveness but it is not enough for locating the sequences.

mRNA results in proteins that are a combination of 20 different amino acids whereas DNA has only four nucleotides, so when gene has similar ancestry, based on amino acid sequences there will more similarity. Hence use of amino acid sequences conclude homology less spuriously.