Can someone please explain this step by step? THanks 18) You sample a large popu
ID: 203803 • Letter: C
Question
Can someone please explain this step by step? THanks
18) You sample a large population of New York City rats for the alleles of two linked genes, A and B. Gene A was found to have two alleles, A1 and A2 where A1 is present at a 20% level (frequency =0.2) and A2 at 80% (frequency = 0.8). Gene B has 3 alleles, B1 present at 80%, B2 at 15% and B3 at 5%. Which measured allele combination in the sample below below most closely approximates the value predicted by linkage equilibrium?
a) A1B1 – 0.65
b) A2B1 - 0.65
c) A1B2 – 0.35
d) A2B2 – 0.95
e) A2B3 – 0.44
Explanation / Answer
let's make a table to check the expected frequency of genotype for linked gene A and B.
A1
(0.2)
A2
(0.8)
B1
(0.8)
A1B1
(0.2x0.8=0.16)
A2B1
(0.8x0.8=0.64)
B2
(0.15)
A1B2
(0.2x0.15=0.3)
A2B2
(0.8x0.15=0.12)
B3
(0.05)
A1B3
(0.2x0.05=0.01)
A2B3
(0.8x0.05=0.04)
In table, A2B1 has expected frequency 0.64 which is very much closer to given option B
therefore, Measured allele combination in the option b is most closely approximates the value predicted by linkage equilibrium
A1
(0.2)
A2
(0.8)
B1
(0.8)
A1B1
(0.2x0.8=0.16)
A2B1
(0.8x0.8=0.64)
B2
(0.15)
A1B2
(0.2x0.15=0.3)
A2B2
(0.8x0.15=0.12)
B3
(0.05)
A1B3
(0.2x0.05=0.01)
A2B3
(0.8x0.05=0.04)