Question

The father of Mr. Spock, second officer of the Starship Enterprise, came from the planet Vulcan; his mother came from the Earth. A Vulcan is homozygous for the genes for pointed ears (P), adrenals absent (A), and a right-sided heart (R). All three genes are dominant over their respective Earth alleles (p, a, and r). These three genes are autosomal and are linked as shown in this linkage map:

P(p)-----------15 map units-----------A(a)---------------20 map units-------------R(r)

If Mr. Spock marries a phenotypically normal Earth woman and there is no genetic interference, what proportion of their children will:

a. have Vulcan ears and Earth adrenals?

b. have Vulcan ears, and Earth adrenals and an Earth heart?

c. look like Vulcans (for all three characteristics)?

d. look like Earth people (for all three characteristics)?

Answer 1

Answer:

a. have Vulcan ears and Earth adrenals = Par/par + Par/par = 6% +8.5% = 14.5%

b. have Vulcan ears, and Earth adrenals and an Earth heart = Par/par = 6%

c. look like Vulcans (for all three characteristics) = 34%

d. look like Earth people (for all three characteristics) = 34%

Explanation:

Father of Mr. Spock (PAR/PAR) x mother of Mr. Spock (par/par)---Parents

PAR/par (volcan)--------------Mr. Spock

PAR/par (Mr. spock) x (normal Earth woman) par/par ---Parents

Expectec double crossover frequency = (Single crossover frequency (SCO) b/w p&a) x (Single crossover frequency (SCO) b/w a&r)

= 15% x 20% = 0.03

Class of gametes	Genotype	Frequency of reciprocal pair	Numbers	Frequency of each class	Number of progeny frequency * 100 = %
Parental	PAR	1- all recombinant progeny	1-(0.12+0.17+0.03) = 0.68	0.34	34% PAR/par (Three characters like volcan)
	par			0.34	34% par/par (Three characters like Earh)
SCO 1	Par	RF in region 1 = SCO1 - DCO	SCO1 = 0.15 – 0.03 = 0.12	0.06	6% Par/par (volcan ear, earth adrenals, earth heart)
	pAR			0.06	6% pAR/par (earth ear, volacn adrenals, volcan heart)
SCO 2	PAr	RF in region 2 = SCO2 - DCO	SCO2 = 0.2 – 0.03 = 0.17	0.085	8.5% PAr/par (volcan ear, volcan adrenal & earth heart)
	paR			0.085	8.5% paR/par (earth ear, earth adrenal & volcan heart)
DCO	PaR	(RF in region 1) * (RF in region 2)	0.03	0.15	1.5% PaR/par (volcan ear, earth adrenal & volcan heart)
	pAr			0.15	1.5% pAr/par (earth ear, volcan adrenal & earth heart)