a local florist is having trouble with a new species of plan

a local florist is having trouble with a new species of plant. She received 2 of these rare plants, 1 of which is really short (5 inches) and the other of which is really tall (23 inches). She would like to sell these plants, but would like them to be medium height (14 inches). When she crosses the plants the F1 progeny are all 14 inches tall. She sells out of these plants very quickly and wants to make more, but the parent plants are no longer fertile. She crosses the F1s with one another and to her surprise she gets plants whose sizes ranged in 3 inch intervals from 5 to 23 inches (5, 8, 11, 14, 17, 20, 23). Most were 14 inches, while 1/64 had 5 inches and 1/64 had 23 inches.

Explain how the plant heights were inherited describing

a) the mode of inheritance

b) indicating how many gene pairs were at work

c) and designating the genotypes of the 2 parental plants, and their 14 inch F1 offspring

d) if one of the 14 inch F1 offspring is mated with one of the 5 inch F2 plants, what phenotypic ratio would be predicted if many offspring resulted?

Solution

(a-c) Lets assume TT=23 inch. and tt=5 inch

TT x tt

F1 Tt Tt Tt Tt (all 14 inch)

Cross among F1

Tt X Tt

TT Tt Tt tt (23, 14,14, 5 inch)

d) if Tt x tt

Tt Tt tt tt

14 inches: 5 inches in ratio

1:1