Need help with genetics problems!

Question

babynini · Answer

"A black, rough male guinea pig is mated to a white, rough female. Out of several litters totaling 27 individuals, 9 are black, rough; 7 are black, smooth; 8 are white, rough; 3 are white, smooth. What are the genotypes of the parents? (Hint: list what is given for the parents and offspring first)"
Also note that: black color coat (B) is dominant to white (b), and a rough coat (R) is dominant to smooth (r)

babynini · Answer

If the dad and mom both are: BbRr 
I know we get the Ratio 9 BR; 3Br; 3 bR; 1br

But i'm not sure how that plays into a total of 27 babies? is it safe to say that the geno types are BbRr?!

mtepecz · Answer

The mom can't be Bb because that would make it black, so what we know for sure is the female is either bbRr or bbRR

babynini · Answer

Ah, good point.

babynini · Answer

If the mom is bbRr and the dad is BbRr
we get a ratio 
3BR;1Br;3bR;1br

babynini · Answer

Yeah I think it's 
Male: BbRr, Female: bbRr
does that look correct? :)

babynini · Answer

Except then the black smooth and white smooth are super close in number..which is not the case.

mtepecz · Answer

That's true, unless the male isn't BbRr and is instaed BBRr

babynini · Answer

but that cannot be the case because then we would never get a br

mtepecz · Answer

Ignore that. It wouldn't work because then all offspring would be all black

babynini · Answer

haha yeah.

babynini · Answer

gaah. What is it then? o.o
That seems like the closest to the wanted results.

mtepecz · Answer

So the parents would be BbRr and bbRr.

babynini · Answer

And the genotypes:
Male: BR, Br, bR, br
Female: bR, br

alphadxg · Answer

Yeah I think it's 
Male: BbRr, Female: bbRr
does that look correct? :)

I agree with this.

babynini · Answer

Yay! thanks you guys.
Yall want to have fun and do more? xP

alphadxg · Answer

;)

mtepecz · Answer

Sure why not, I'm a bio major for a reason.

babynini · Answer

xD ok so it's with the same guinea pig thing.

BBRR x bbrr:
Phenotype: ?
Genotype: ?

babynini · Answer

So.. I think 
Phenotype: BR, br
Genotype: BbRr

is that how that works?

alphadxg · Answer

post it on a new post, close this one.

mtepecz · Answer

Correct!

babynini · Answer

yay!