In the snail cepaea nemoralis, an autosomal allele causing a banded shell (bb) is recessive to the allele for unbanded shell (bo). genes at a different locus determine the background color of the shell; here, yellow (cy) is recessive to brown (cbw). a banded, yellow snail is crossed with a homozygous brown, unbanded snail. the f1 are then crossed with banded, yellow snails (a testcross).a. what will the results of the testcross be if the loci that control banding and color are linked with no crossing over?
b. what will the results of the testcross be if the loci assort independently?
c. what will the results of the testcross be if the loci are linked and 20 m. u. apart?

a) As a result of the testcross when the loci that control banding and color are linked with no crossing over, then the F2 testcross progeny will be half banded, yellow and half unbanded, brown.

b) As a result of the testcross if the loci are assorted independently, the progeny formed would be:

c) In case of the conclusionof the testcross, if the loci are linked and 20 m.u. apart then,

the farther away the object is from the central star (the sun) it's gravitainal pull on the object is weaker when it is farther

explanation:

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.