three stop codons TAG, TAA, TGA, and one start codon ATG.
without getting into exons and introns, proteins start with an ATG in the DNA. the protein is ended with a stop codon. looking at other amino acid codons, it's easy to see that if a TAG had a mutation in the third position that was not a G or an A, the protein would keep extending from the DNA (yes i left out a step for clarity). conversely, if an amino acid was converted from a C or T in the third position, it would stop prematurely, and you would get a defective protein, and PHA or whatever. yes, you can have mutations at different spots in different animals and the symptoms could be slightly different. mutations in postitions which don't change the amino acid are called silent and other words. yes, there is a lot going on, it's sometimes amazing we are even alive to argue about this.
the point mutation doesn't normally move around, as it usually doesn't have enough time to do that as the generation interval in cattle is so long. this is overcome slightly when a carrier bull gets used on thousands of individuals. in some frogs and plants, there are massive rearrangements upon union of gametes, but within the genes is pretty static, and the defective one's just die. it's easy to see why it's real easy to get genetic freaks from these types of organisms that aren't lethal.
the example below doesn't include alternative starts and other scenarios for other explanations. both strands are shown.
stop (premature) stop (normal stop)
ATG GCA CGT ACG TAC TGA TCG TAT CGG GAC GAT ATC GGT ACG ATC GAT CGT ACG TAC GTG GTG TAC TGT TCG TGT CTC TAA defective calf
ATG GCA CGT ACG TAC TGA TCG TAT CGG GAC GAT ATC GGT ACG ATC GAT CGT ACG TAC GTG GTG TAC TGT TCG TGT CTC TAA
ATG GCA CGT ACG TAC TGA TCG TAT CGG GAC GAT ATC GGT ACG ATC GAT CGT ACG TAC GTG GTG TAC TGT TCG TGT CTC TAA carrier calf
ATG GCA CGT ACG TAC TGC TCG TAT CGG GAC GAT ATC GGT ACG ATC GAT CGT ACG TAC GTG GTG TAC TGT TCG TGT CTC TAA
ATG GCA CGT ACG TAC TGC TCG TAT CGG GAC GAT ATC GGT ACG ATC GAT CGT ACG TAC GTG GTG TAC TGT TCG TGT CTC TAA defect free calf
ATG GCA CGT ACG TAC TGC TCG TAT CGG GAC GAT ATC GGT ACG ATC GAT CGT ACG TAC GTG GTG TAC TGT TCG TGT CTC TAA
as you can see, base pairs in general don't really move around on an individual basis, though multiple ones (not shown) can and do causing problems.
if there was a base pair change before the correct stop, or a deletion or insertion of basepairs, this would be a second defective allele, and yes, requires a separate test, like in TH.
i didn't go over the above, so there may be a mistake, so feel free to correct.
). I am glad we have the test for everyone to use and the hard work put in by all those involved (some right here on the Planet too). And I love the rules the RA has made.
