A certain plant is 2n 8 The complement of chromosomes consi

A certain plant is 2n = 8. The complement of chromosomes consists of a long metacentric pair, a short metacentric pair, a long telocentric pair, and a short telocentric pair. After three generations of self-fertilization, what percent of the progeny will have ... four pairs of telocentric chromosomes? two pairs of metacentric and two pairs of telocentric chromosomes?

Solution

Plant is 2n=8. This situation can be compared with a tetrahybrid cross with 4 trait (Long metacentric pair, short metacentric pair, long telocentric pair and short telocentric pair). Suppose we are representing this with some letters,

i.e Long metacentric = AA

Short metacentric =aa

Long telocentric= BB

Short telocentric=bb

So the cross will be AAaaBBbb x AAaaBBbb

So after three generations, the total number of progenies = (16)³

a) The percentage of getting four pairs of telocentric chromosomes is zero.(0%).Because the produced gametes surely will have A, a, B,b (4 gametes). So no chances of getting 4 pairs of telocentric, defenitely one pair will be metacentic.

b) After three generations, only one distinct progeny will be produced with two pairs of metacentric and two pairs of telocentric.(i.e. AAaaBBbb). So the percentage is 100%