In cucumbers, heart-shaped (hs) leaves are recessive to normal leaves (HS) & spi
ID: 62915 • Letter: I
Question
In cucumbers, heart-shaped (hs) leaves are recessive to normal leaves (HS) & spineless (ss) fruit is recessive to fruits with spines (SS). The genes for leaf shape & spines are located on the same chromosome & experimental findings suggest these loci are 28.2 M.U. apart. A cucumber homozygous for the dominant traits is crossed to one that is homozygous recessive for the recessive traits. The F1 progeny are then testcrossed. If 620 progeny are produced, what phenotypes, & in what proportions would progeny be produced?
Explanation / Answer
heart-shaped leaves (hs); normal leaves (HS); fruit spineless (ss); fruits with spines (SS).
The genes for leaf shape & spines are 28.2 M.U. apart
HSHSSSSS X hshsssss
HShsSSss (F1 progeny)
HShsSSss x hshsssss (Test cross)
hsss
hsss
hsss
hsss
HSSS
HShsSSss
HShsSSss
HShsSSss
HShsSSss
HSss
HShsssss
HShsssss
HShsssss
HShsssss
hsSS
hshsSSss
hshsSSss
hshsSSss
hshsSSss
hsss
hshsssss
hshsssss
hshsssss
hshsssss
Parental: HShsSSss (normal leaves, fruit with spines) = 4 / 16 = 25 %
Recombinant: HShsssss (normal leaves, fruit spineless) = 4 / 16 = 25 %
Recombinant: HshsSSSS (heart shaped leaves, fruit with spines) = 4 / 16 = 25 %
Parental: Hshsssss (heart shaped leaves, fruit spines) = 4 / 16 = 25 %
So, expected ratio is 1: 1 :1 :1
Observed Recombination frequency (total number of recombinants) = 28.2 %
Hence, out of 620 progeny
14.0 % (normal leaves, fruit spineless) = 87.42
14.0 % (heart shaped leaves, fruit with spines) = 87.42
36.0 % (normal leaves, fruit with spines) = 222.58
36.0 % (heart shaped leaves, fruit spines) = 222.58
Observed ratio = 1 : 1 : 3 : 3
hsss
hsss
hsss
hsss
HSSS
HShsSSss
HShsSSss
HShsSSss
HShsSSss
HSss
HShsssss
HShsssss
HShsssss
HShsssss
hsSS
hshsSSss
hshsSSss
hshsSSss
hshsSSss
hsss
hshsssss
hshsssss
hshsssss
hshsssss
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.