When truebreeding mice with brown fur and short tails BBtt w

When true-breeding mice with brown fur and short tails (BBtt) were crossed to true- breeding mice with white fur and long tails (bbTT), all F1 offspring had brown fur and long tails. The F1 offspring were crossed to mice with white fur and short tails. What are the possible phenotypes of the F2 offspring? Which F2 offspring are recombinant, and which are parental? What are the ratios of the F2 offspring if independent assortment is taking place? How would the ratios affected by linkage?

Solution

Here, a true breeding mice with brown fur and short tails (BBtt) is crossed with a true breeding mice with white fur and long tails (bbTT), the F1 crossing is illustrated below:

Brown fur, short tail X White fur, Long tail

BBtt X bbTT

gametes ........... Bt, Bt, Bt, Bt bT, bT,bT, bT

F1 Generation ....................... BbTt (All are brown fur,long tails)

Let us see if F1 crossed with White fur and Short Tails (bbtt),

Brow fur , long tail (F1) X White fur, short tail

BbTt X bbtt

gametes............... BT, Bt, bT, bt bt

F2 Generation ............... BbTt , Bbtt, bbTt, bbtt

Brown fur, long tail (F1) X White fur , short tail

BbTt X bbtt

gametes................BT, bt bt

F2 Generation .......................... BbTt, bbtt

( Brown fur , Long tail, white fur, short tail )

Ratio of the offspring will be 1:1.