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?

1) The possible phenotypes of the F2 offspring are: brown fur, short tails; brown fur, long tails; white fur, short tails; and white fur, long tails.

2) The F2 offspring that are recombinants: brown fur, long tails, and white fur, short tails.

The parental are: brown fur, short tails, and white fur, long tails.

3) The ratio of F2 offspring if independent assortment is taking place will occur in a 1:1:1:1 ratio .

4) if linked, there will be a lower percentage of the recombinant offspring.

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.