1 In dolphins gray G is dominant to black g Sleek S is domin

1. In dolphins, gray (G) is dominant to black (g), Sleek (S) is dominant to pudgy (s) and friendly (F) is dominant to mean (f). All loci are autosomal. Pure-breeding black, sleek , mean dolphins were mated to pure-breeding gray, pudgy, friendly dolphins. The F1 were testcrossed. Based on the map below and a coefficient of coincidence of 0.7, determine the frequency of each phenotype in the testcross progeny. Round each answer to 5 decimal digits.

(a) What is the frequency of gray, sleek testcross progeny?

(b) What is the frequency of pudgy, mean testcross progeny?

(c) What is the frequency of gray, friendly testcross progeny?

(d) What is the frequency of pudgy, friendly testcross progeny?

(e) What is the frequency of black, friendly testcross progeny?

(f) What is the frequency of black, pudgy, mean testcross progeny?

(g) What is the frequency of gray, sleek, mean testcross progeny?

(h) What is the frequency of gray, pudgy, friendly testcross progeny?

Solution

The Crosses will be as follows:

ggSSff X GGssFF --> GgSsFf = F1 Progeny

GgSsFf X ggssff --> Testcross progeny

According to the given Map, the distances can be correlated to the respective recombination frequencies. Let colour be \'C\', Body type \'BT\' and Disposition \'D\'.
The frequency of double cross overs (DCO) = (Recomb. frequency of C-BT) * (Recomb. frequency of BT-D)
   = 0.24*0.05 = 0.012 = 1.2%
It means that 0.6% would be ggSsff and 0.6% would be GgssFf.

The frequency of single cross over (C-BT) = Recomb. frequency - frequency of DCO
   = 5 - 1.2 = 3.8%
It means that 1.9% would be ggSsFf and 1.9% would be Ggssff.

The frequency of single cross over (BT-D) = Recomb. frequency - frequency of DCO
   = 24 - 1.2 = 22.8%
It means that 11.4% would be ggssFf and 11.4% would be GgSsff.

The total recombinants come out to be 27.8% and remaining are parental combinantions with 72.2% frequency implying 36.1% of each parental type (GgSsFf and ggssff).

We know coefficient of coincidence (COC)= Observed frequencies/expected frequencies. We know, COC= 0.7 and we have calculated the expected frequencies.

So, observed frequency = COC * Expected frequency:

a) Genotype GgSs = 11.4 + 36.1 % = 47.5% So, expected frequency = 47.5*0.7 = 33.25%

b) Genotype ssff =1.9 + 36.1 % = 38.0% So, expected frequency = 38.0*0.7 = 26.6%

c) Genotype GgFf = 0.6 + 36.1 % = 36.7% So, expected frequency = 36.7*0.7 = 25.69%

d) Genotype ssFf = 11.4 + 0.6 % = 12.0% So, expected frequency = 12.0*0.7 = 8.4%

e) Genotype ggFf =1.9 + 11.4 % = 13.3% So, expected frequency = 13.3*0.7 = 9.7%

f) Genotype ggssff= 36.1 % So, expected frequency = 36.1*0.7 = 25.27%

g) Genotype GgSsff=11.4 % So, expected frequency = 11.4*0.7 = 7.98%

h) Genotype GgssFf=0.6 % So, expected frequency =0.6*0.7 =0.42%