Question

In: Biology

6. Two true breeding varieties of plants are crossed in a two-factor cross. One parent has...

6. Two true breeding varieties of plants are crossed in a two-factor cross. One parent has red axial flowers and the other had white terminal flowers. All F1 individuals had red terminal flowers. The F1 offspring are then crossed to produce the F2 offspring.

a. Which traits are dominant? Which are recessive? What are the genotypes of the F1 individuals?

b. If 300 F2 offspring were counted, how many of them would you expect to have red, axial flowers. Show your work, including a Punnett square.

Solutions

Expert Solution

6) a) Two true-breeding varieties of plants are crossed in a two-factor cross. One parent has red axial flowers and the other had white terminal flowers all the F1 progenies had red terminal flowers, so red flower colour and terminal flowers are dominant phenotypes.

b) let the alleles be R- red, r- white, T- terminal, t- axial.

RRTT * rrtt

RrTt

RrTt * RrTt

RT Rt rT rt
RT RRTT ( red, terminal flowers) RRTt ( red, terminal flowers) RrTT ( red, terminal flowers) RrTt ( red, terminal flowers)
Rt RRTt ( red, terminal flowers) RRtt ( red axial flowers) RrTt ( red, terminal flowers) Rrtt( red axial flowers)
rT RrTT ( red, terminal flowers) RrTt ( red, terminal flowers) rrTT (white, terminal flowers) rrTt (white, terminal flowers)
rt RrTt ( red, terminal flowers) Rrtt( red axial flowers) rrTt (white, terminal flowers) rrtt ( white axial flowers)

the proportion of red axial flowers= number of plants with red axial flowers/total number

= 3/16

expected number of plants with red axial flowers out of 300 plants= 300 proportion of red axial flowers

= 300 3/16

=56.25

expected number of plants with red axial flowers out of 300 plants = 56


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