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ilovelifex ilovelifex
wrote...
Posts: 18
Rep: 1 0
11 years ago
both parent dogs are solid black. their puppies, however have 4 different phenotypes as listed below:
-solid black
-black & white spots
-solid red
-red & white spots
which of the following explains how these parent dogs can produce puppies with these 4 phenotypes?
a) genes are sex-linked
b) genes for these traits mutate frequently
c) the genes for these traits assort independently
d) genes for these traits are  on the same chromosomes.

I know this is long.. sorry.
Thank you:)
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wrote...
11 years ago
I'm not 100% sure but i would think its B
wrote...
11 years ago
The genes are sex linked. The parrents may bea llblack, but they could hold teh recessive genes for different colors.

or the mom could be getting ourd =P hahaha jk
wrote...
11 years ago
This can only occur whereby there is an improper change in the process of reproduction, this is irregular but it can occur though not frequently so i guess the answer to your question is; genes for these traits mutate.
wrote...
11 years ago
The answer is C.
As there are more than one pair for the fur color and spotting and they should be assort independently.
wrote...
11 years ago
The question tells you that the parents are heterozygous for two traits, so this rules out answer a (the male parent can't be heterozygous, but could only be hemizygous, since there is only one X chromosome).  Generally in mammals, genes don't mutate frequently, so you can ignore answer b.  If the genes were on the same chromosome (and close together), then you would have a lot of puppies that look like the parents and a few recombinants that have different phenotypes from the parents.  Since the question didn't talk about this at all, then answer d is not the answer.  This leaves answer c as the correct answer.  Here is why:

If black is B and red is b, non-spotting is S and spotting is s, then the parents are:

BbSs  x  BbSs

The offspring would be in the following 9:3:3:1 ratio:

9 B-S-, black, non-spotted
3 bbS-, red, non-spotted
3 B-ss, black, spotted
1 bbss, red, spotted

This result occurs if the genes are separate genes and unlinked.  The ratios would be somewhat different if the genes were linked, but the four phenotypes would likely all show up.  So, the best answer is c.
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