A white mouse whose parents are both white produces only brown offspring when mated with a brown mouse.?

Question

the white mouse is most probaly:
A) homozygous recessive
B) Heterozygous
C) Homozygous dominant
D) Haploid

Answer 1

A)

The white mouse shares the phenotype and genotype of parents

Mother white mouse: aa
Father white mouse: aa
White mouse: aa

The Brown mouse might be 2 things,
either heterozygous: Aa
or homozygous dominant: AA

(in these type of exercises, when you mate something with an animal from which you have no info, he's usually homozygous. And if he wasn't the next step would not work.)

Therefore, the mating of the white mouse (aa) with the brown mouse (AA) give only heterozygous (Aa) brown mice.

Why not B?
Because if the white mouse was heterozygous (Bb), that meant that "White" was the dominant gene, and the brown mouse had to be homozygous recessive (bb). But now you can say that they still could have a brown mice offspring, because they both carry a recessive allele (bb). Well, yes, but eventually white mice would appear in the be born (BB, Bb). This way it would never be all brown.

Why not C?
Because all the offspring would then be all white and never brown. It's the inverse of example A).

Why not D?
Because the white mouse is alive and fertile.

Answer 2

Since each parent contributes half their DNA to the offspring, there should be 4 possible outcomes. The only way that all 4 outcomes have the same result is if both parents are homozygous.

Since white is never expressed, it must be recessive:
http://en.wikipedia.org/wiki/Homozygous

Answer 3

let's imagine that each and all of the mice mothers and dads have a recessive brown gene. you're able to finally end up with: mom Ww Dad Ww enormous W being the white Gene and little w being the brown gene (or non white gene) you're able to get the sq. W w W= WW Ww w= Ww ww <------ so which you're able to have a three to a million hazard of having a white offspring. so there's a one in 4 hazard which you're able to have a clean brown toddler mouse besides. desire this enables

Answer 4

homozygous recessive
only a guess but I studied genes and heredity for a while

Answer 5

b)heterozygous
Ww crossed with Ww

Answer 6

A I think, we just learned this a few weeks ago, but I can't remember...

Answer 7

E, has down syndrome

Answer 8

A

Answer 9

A