The father of Mr. Spock, first officer of the starship Enterprise, came from pla

Question

The father of Mr. Spock, first officer of the starship Enterprise, came from planet Vulcan; Spock's mother came from Earth. A Vulcan has pointed ears (determined by allele P), adrenals absent (determined by A), and a right-sided heart (determined by R). All these alleles are dominant to normal Earth alleles. The three loci are autosomal, and they are linked as shown in this linkage map:

If Mr. Spock marries an Earth woman and there is no (genetic) interference, what proportion of their children will have

a.Vulcan phenotypes for all three characters?

b.Earth phenotypes for all three characters?

c.Vulcan ears and heart but Earth adrenals?

d.Vulcan ears but Earth heart and adrenals

Explanation / Answer

Answer: The cross is Spock PAR/par x wife par/par

a) 15% crossing over occurs between P and A (which as does not occur 85% of the time)

20% crossing over occurs between A and R (which does not occur 80% of the time)

p (no crossover between P and A) (no crossover between A and R)

(0.85) (0.80)= 0.68, as half of the parentals are Vulcan and earth alleles, the frequency of children with vulcan is

1/2(0.68)=0.34.

b) if 0.34 inherit vulcan characters, then 0.34 inherit earth characters.

c) in order to get vulcan ears and heart but earth adrenals, a cross over should occur in both regions, the frequency will be half the double crossing over

1/2(0.15)(0.20)=0.015

d) in order to get vulcan ears but earth heart and adrenals, single crossing over in offspring. this is calculated as crossing over frequency minus double crossing over

p (CO P-A)xp(no COA-R)= (0.15)(0.80)=0.12

of these 1/2 are Par and 1/2 are pAR. so the proportion to get vulcan ears but earth heart and adrenals is

0.12/2=0.06.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.