Genetics - homework help, read for info.?

Question

A protein is coded by a eukaryotic gene containing two introns and three exons in that order:

exon 1 – intron 1 – exon 2 – intron 2 – exon 3

Which mutation is more likely to cause severe disruption in the synthesis of this protein?
a)A deletion of six bases in the centre of intron 2
b)A transversion in exon 2
c)A frameshift mutation in exon 1
Justify your answer.

Answer 1

In this question, they're testing 2 key points -- do you know what introns and exons are, and do you know which type of mutation is the worst.

Exons and Introns are different pieces of DNA where introns don't code for anything, whereas exons do. So an easy way to remember that is EXons are EXpressed. (the DNA code is like this as a safeguard from mutations--since when DNA replicates there is so much to replicate, and to prevent many errors it has a lot of buffer material (the introns), so it is less likely that something important well have a mutation since only 5% of all the info is important (the exons).

so, a is obviously out since introns don't contribute to anything.

b) transversion v. frameshift. Transversions are when 2 base pairs get flipped. Frameshift mutations are when the reading frame gets shifted. If you have a transversion, it is okay because either 1 or 2 proteins max will change. However, if you have a frameshift mutation, then you can have stops where u have starts, or starts where you have stops, and that is much worse, so you would get a much worse outcome if you were to have a frameshfit mutation.

so C is the worst.

Answer 2

A mutation such as in (A) can result in a severe defect. In many diseases there are mutant alleles that are splice defects. If the six bases that are removed in A are in an intronic splicing enhancer signal, that could result in a misprocessed mRNA with a different message or a one that is degraded.

Do your own homework.

Answer 3

Jesse is right. "b" won't matter, it's an exon. "a" will result in the elimination of two amino acids and there's the possibility that the protein will still work. "c" screws it up royally.

Answer 4

c. frameshift mutation by insertion or deletion of single nucleotide base can result in codons encoding different proteins in the downstream processes from the point of mutation.

Answer 5

I don't know. Do your own homework.

Answer 6

are you asking us to do your homework?