Biology-Online • View topic - homework. I just need somebody to check my answer for me.

homework. I just need somebody to check my answer for me.

Genetics as it applies to evolution, molecular biology, and medical aspects.

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homework. I just need somebody to check my answer for me.

let's say you have 9 black mices, 19 black and white mices and and 14 white mices. black is dominant to white.
1) what phenotypic ratio is observed setting the lowest number to one: black? white and black? white?
I answered: 2 Black/white : 1 White : 1 Black. is that correct? 1:2:1 ration. or is it 3:1

2) what is the most likely genotype for each phenotype observed
I answered: B=black and b=white:
pure black BB
black/white Bb
pure white bb

3) you have 3 phenotypes present in these mice what genetic condition would result in this kind of segregation? ans: epistasis, but I am not sure and I don't think it's right.
herm2020
Garter

Posts: 2
Joined: Thu Sep 22, 2011 8:46 pm

Something's not right here. What you're describing is not a dominant - recessive situation.
Darby
Viper

Posts: 1278
Joined: Thu Mar 02, 2006 5:29 pm
Location: New York, USA

1) probably yes. With such low numbers, you won't get the exact ratio

2) I would say yes, but you said, that black is dominant over white.
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JackBean
Inland Taipan

Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm

i would say that you have a ratio of 9:19:14

so setting the lowest number to one (9, thus divide them all by 9) you get:
1:2.1:1.5 (answers to 1 decimal place)

is this a high school question? if so, then the answer you have given looks good. It higher level, you might be looking at a complex genetic phenomena. However, the question does not even say that these are the offspring of two parents - which is important to know.

As far as I know, the phenomenom of coat colour that you are describing is agouti - and it is a complex epistatic phenomenon (you are correct for question 3). As far as I know, crosses between black and albino mice yields 3:1 black mice to white - and there are no black and white mice in such crosses.

Hope that helps.
merv