1) Flower beetles with thedominant allele R have black wings, whereas beetles th
ID: 4939 • Letter: 1
Question
1) Flower beetles with thedominant allele R have black wings, whereas beetles thatare homozygous for the recessive allele r have red wings.A second, independently assorting gene also influences wing color.The dominant allele C of this gene encodes a protein thatprevents any pigment from being deposited in the wings. As aresult, beetles bearing this dominant allele have colorless wings.A beetle with genotype CC RR is crossed with anotherbeetle having genotype cc rr. Their offspring are thenintercrossed to produce an F2 generation. Whatphenotypes are expected in the F2 plants, and in whatproportions?
Explanation / Answer
dominant allele -R
recessive allele---------r
beetles that arehomozygous(rr) for the recessive allele r - redwings
dominant allele Cgene ----------encodes a protein that prevents any pigment frombeing deposited in the wings. As a result, beetles bearing thisdominant allele have colorless wings
CCRR x cc rr.
CR cr-----------gametes
CcRr----------colorless
Cc Rr----------colorless x CcRr----------colorless
CR Cr cR cr CR Cr cR cr----gametes
C R
Cr
cR
cr
C R
C R C R colorless
C R Cr colorless
C R cR colorless
C R cr
colorless
Cr
C R Cr colorless
Cr Cr
colorless
Cr cR
colorless
Cr cr
colorless
cR
C R cR colorless
Cr Cr
colorless
cR cR
black wings
cR cr
black wings
cr
C R cr
colorless
Cr cr
colorless
cR cr
black wings
cr cr
red wings
Colorless: blackwings :red wings = 12:3:1
C R
Cr
cR
cr
C R
C R C R colorless
C R Cr colorless
C R cR colorless
C R cr
colorless
Cr
C R Cr colorless
Cr Cr
colorless
Cr cR
colorless
Cr cr
colorless
cR
C R cR colorless
Cr Cr
colorless
cR cR
black wings
cR cr
black wings
cr
C R cr
colorless
Cr cr
colorless
cR cr
black wings
cr cr
red wings
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