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in flour beetles, pygmy (py) is recessive to normal size (py+) and red color (r) is...

in flour beetles, pygmy (py) is recessive to normal size (py+) and red color (r) is recessive to brown (r+). A beetle heterozygous for these characteristics was testcrossed to a red pygmy beetle. The table below shows the numbers and phenotypes from the progeny of this testcross - use this information to answer the following three questions. Progeny phenotype Progeny number

Normal size, brown 180

Normal size, red 20

Pygmy, brown 10

Pygmy, red 190

Total 400 Flag this Question

Question 21. What is the recombination frequency between py and r? Please express your answer as number (no words), in units of centimorgans.

Question 22. If these two genes were completely unlinked, how many progeny (out of 400) would we expect in each phenotypic class in the table above? Express your answer as a number (no words).?

Solutions

Expert Solution

21) recombination frequency in the percentage of recombinant progenies.

maximum recombination frequency between genes is 50%, if the recombination frequency is 50% then the genes are not linked.

if the genes are linked on a chromosome we expect few recombinant progenies than non-recombinant progenies.

here the number of Normal size, red beetles and Pygmy, brown beetles are less than that of the other two phenotypic classes so Normal size, red beetles and Pygmy, brown beetles are recombinant progenies.

recombination frequency= (number of recombinant progenies/total number of progenies)100

= (( number of Normal size, red + number of Pygmy, brown)/total number of progenies)100

= ( (10+20)/400)100)

= 7.5 %

recombination frequency is the distance between genes in cM

so the answer is 7.5 cM

22) if the genes are unlinked

py+py r+r * pypyrr

	py+r+	py+r	pyr+	pyr
pyr	py+r+/pyr ( normal size brown)	py+r/pyr ( normal size red)	pyr+/pyr ( pygmy, brown)	pyr/pyr( pygmy, red)

if the genes are not linked all the phenotypes are expected in equal proportion.

Normal size, brown: Normal size, red : Pygmy, brown: Pygmy, red = 1:1:1:1

all the phenotypes are expected in equal proportion that is 1/4 each.

Normal size, brown= 4001/4=100

Normal size, red = 4001/4=100

Pygmy, brown = 4001/4=100

Pygmy, red = 4001/4=100

gladiator answered 1 year ago

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