Question

black fur in mice(B) is dominant to brown colour(b).short tails(T) are dominant to long tails(t).what fraction of progeny of the cross between BbTt and BBtt will have black fur and long tails

Answer 1

         B          b

B        BB       Bb

B        BB        Bb  

100% chance of black fur

         T            t

t          Tt          tt

t         Tt           tt

50% chance of long tails

1 x 1/2 = 1/2 or 50% chance of black fur and long tails.

i hope the punnet squares helped you to understand.

Answer 2

50% of organisms will be of character black fur and long tails.

Explanation:

The given cross is a type of back cross where an organism of f1 generation is crossed with a recessive parent .

The  result will be 50% BbTt and 50% BBtt.