In sheep, coat color is influenced by two genes. Gene A influences pigment production, while gene B produces black or brown pigment. If two heterozygous white sheep were crossed and offspring were produced in a ratio of 12 white sheep to 3 black sheep to 1 brown sheep, what are the genotypes of the offspring?A) The white sheep could be A-B- or aaB-.
B) The white sheep could be A_B_ or aabb.
C) The white sheep could be A_B_ or A_bb.
D) The white sheep must all be aabb.
E) The white sheep must all be A_B_.

C) The white sheep could be A_B_ or A_bb.

Explanation:

Given that in a certain population of sheep, coat color is influenced by two genes, in which:

Gene A: influence pigment production

Gene B: influence black or brown pigment.

Since Gene B influences Black or Brown pigment production and we are given three coat color (white, black and brown), definitely, this implies that Gene A influences White  pigment production.

NOW, If two heterozygous sheep were crossed; definitely we knew our heterozygous genes will be AaBb, so if two of these were crossed;

Offspring that were produced were in the ratio of 12 white: 3 black : 1 brown

So, we are asked to deduce, what is the possible genotype of the offspring:

If a cross occur between AaBb:

i.e AaBb × AaBb

we have the following gametes for the cross: (AB, Ab, aB, ab)

                 AB                       Ab                 aB                     ab

AB            AABB                 AABb              AaBB                AaBb

Ab            AABb                  AAbb              AaBb                Aabb

aB            AaBB                   AaBb              aaBB                aaBb

ab            AaBb                   Aabb                aaBb               aabb

So, since gene A influences white pigment production; if can either be A_B_ or A_bb.

Since gene B influences black or  brown pigment production;

then aaB_ represent Black sheep

and aabb represent homozygous recessive Brown sheep.

So for white sheep; we have the following gene:

( AABB, AABb, AaBB, AaBb, AABb, AAbb, AaBb, Aabb, AaBB, AaBb, AaBb, Aabb ) = 12

Black sheep = (aaBB, aaBb, aaBb) = 3

Brown = (aabb) = 1

Therefore, The white sheep could be A_B_ or A_bb.

answers are:

lysogenic     viral dna merges with host cell dna

lysogenic     no symptoms

lytic               viral dna takes over

lysogenic     virus does not destroy host cell

lytic               virus destroys host cell

lytic               induces symptoms of viral infection

lysogenic       cell reproduces and spreads provirus

occluded front i think