Time for some more xenobiology In aliens glossy exoskeleton

Time for some more xenobiology. In aliens, glossy exoskeleton (G) is dominant to dull exoskeleton (g), excessive drooling (D) is dominant to normal drooling (d), and highly acidic blood (A) is dominant to mildly acidic blood (a). Genetic researchers at Weyland-Yutani Corporation perform a three-point testcross to map the relative locations of these genes. They crossed heterozygotes for all three traits with recessive homozygotes and collect this data:

Observed Number

Glossy, excessive drooling, highly acidic

Dull, normal drooling, mildly acidic

Glossy, excessive drooling, mildly acidic

Dull, normal drooling, highly acidic

Glossy, normal drooling, highly acidic

Dull, excessive drooling, mildly acidic

Glossy, normal drooling, mildly acidic

Dull, excessive drooling, highly acidic

a)Which progeny are the nonrecombinants?

b)Which progeny are the double crossovers? What is the gene order?

c)In the Table, assign genotypes to each of the phenotypes using linkage notation.

d)Calculate the recombination frequencies and draw the genetic map showing the correct gene order and distances between genes.

Calculate the coefficient of coincidence.

Calculate the interference value.

		Observed Number
Glossy, excessive drooling, highly acidic		43
Dull, normal drooling, mildly acidic		36
Glossy, excessive drooling, mildly acidic		13
Dull, normal drooling, highly acidic		4
Glossy, normal drooling, highly acidic		333
Dull, excessive drooling, mildly acidic		303
Glossy, normal drooling, mildly acidic		130
Dull, excessive drooling, highly acidic		138
		1000

Solution

Answer:

Phenotypes

Short hand genotypes

Observed Number

Glossy, excessive drooling, highly acidic

GDA

43

Dull, normal drooling, mildly acidic

gda

36

Glossy, excessive drooling, mildly acidic

GDa

13

Dull, normal drooling, highly acidic

gdA

4

Glossy, normal drooling, highly acidic

GdA

333

Dull, excessive drooling, mildly acidic

gDa

303

Glossy, normal drooling, mildly acidic

Gda

130

Dull, excessive drooling, highly acidic

gDA

138

1000

Imaginary order is GdA/gDa

1.    If single cross over (SCO) occurs between G & D

Normal order= G---------d & g-----D

After cross over= G-----D & g------d

G-----D recombinants are 43 + 13 = 56

g------d recombinants are 36+ 4 = 30

Total recombinants = 86

RF = (86/1000.)*100 =8.6%

2.    If single cross over (SCO) occurs between d & A

Normal order= d---------A & D----a

After cross over= d-----a & D------A

d-----a recombinants are 130+36 = 166

D------A recombinants are 138+43 = 181

Total recombinants = 347

RF = (347/1000)*100 = 34.7%

3.    If single cross over (SCO) occurs between G & A

Normal order= G---------A & g------a

After cross over= G-----a & g------A

G-----a recombinants are 13+ 130 = 143

g------A recombinants are 4+ 138= 142

Total recombinants = 285

RF = (285/1000)*100 =28.5%

% RF = Map unit distance

The order of genes is -----

d---8.6 m.u.---G-------28.5 m.u.--------A

a). Non recombinant progeny are

Glossy, normal drooling, highly acidic & Dull, excessive drooling, mildly acidic

b). The double crossover progeny are

Glossy, excessive drooling, mildly acidic & Dull, normal drooling, highly acidic

The gene order is d---8.6 m.u.---G-------28.5 m.u.--------A

dGA/Dga (normal)

After double crossover, the order is dgA/DGa

d).

RF between d & G = 8.6% = 0.086

RF between G & A = 28.5% = 0.285

RF between d & A = 34.7% = 0.347

RF = distance between the genes

The gene order is d---8.6 m.u.---G-------28.5 m.u.--------A

Expected double cross overs = 0.086 * 0.285 = 0.025

Observed double cross overs = 0.013 + 0.004= 0.017

Coefficent of coincidence (COC) = Obeserved dco / Expected dco

COC = 0.017/0.025 = 0.68

Interference = 1-CC = 1-0.68 = 0.32

Phenotypes	Short hand genotypes	Observed Number
Glossy, excessive drooling, highly acidic	GDA	43
Dull, normal drooling, mildly acidic	gda	36
Glossy, excessive drooling, mildly acidic	GDa	13
Dull, normal drooling, highly acidic	gdA	4
Glossy, normal drooling, highly acidic	GdA	333
Dull, excessive drooling, mildly acidic	gDa	303
Glossy, normal drooling, mildly acidic	Gda	130
Dull, excessive drooling, highly acidic	gDA	138
		1000