Question 28

[shaun.w.mc6504]

I may not be seeing this clearly but how come it is only 6 different peptides?

You have three amino acids A,B,C

AAA
BBB
CCC
ABC
ABB
ACC
ACB
AAC
AAB
ABA

The list goes on? What am I missing here.

[admin]

Most students will interpret the question to mean that each tripeptide must contain the 3 different amino acids which limits the total to 6. If you did not have that interpretation initially, after some determination as you did above, you would quickly notice that you get a figure far beyond any of the answer choices which would guide you to reinterpret any assumptions.

Most importantly: every 2-3 real MCATs, you will see a similar concept tested. The result can't be a huge number because they are testing concepts not your ability to calculate.

[admin]

bump

[aaron.lam3624]

no way, most students who have taken any type of college level genetics should be trained to think that amino acids can repeat, thats the beauty of the codon system. So much variability from so few amino acids.

This question is in the gray area. It would be better to specify that each amino acid can only be used once, otherwise there are 27 possibilities. Which is not a hard number to calculate as suggested by the admin post, 3x3x3=27. AAB is as distinct peptide from AAA, exactly as the question asks. I was given this exact question on a college genetics test and the answer was 27.