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Phenotype and genotype ratios

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

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Phenotype and genotype ratios

Postby kngeorges » Sun Jan 10, 2010 1:38 am

I understand that phenotype and genotype ratios are fairly similar, i just have an extremely confusing question and cannot find the answer anywhere. ex of problem: BB Bb Bb Bb. which means that they are all black . . . so how do i put that in a ratio? i know that you can put that in a percent but my paper asks for a ratio and i have no idea how to do it.
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Postby mith » Sun Jan 10, 2010 3:52 am

you need something to compare it to for it to be a ratio, since there's only one type your phenotype "ratio" would just be one, I wouldn't get too hung up on that answer, write an explanation if you feel like your grader might give you trouble about it. However, your genotype ratios would definitely be a ratio.

Edit, there's no crossing that would give you BB, Bb X3. So you might have made a mistake somewhere.
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Postby JackBean » Sun Jan 10, 2010 11:43 am

I guess, your genotypes are BB, Bb, Bb, bb. So, the phenotypic ratio varies in dependence of dominance/recessivity ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby vijeta » Fri Feb 12, 2010 10:20 am

I think you can write it as 1 homozygous black(BB):3 heterozygous black(Bb)
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Re: Phenotype and genotype ratios

Postby UhmYeah » Tue Apr 20, 2010 12:08 am

Okay, I have a little project for class and I have two questions to ask you:

1. You said that if all the outcomes are the same (I have a tetrahybrid cross -256 squares- and it is a cross between true-breeding parents. EEWWHHCC and eewwhhcc) I would put Mendel's law of informity or whatever for the genotype ratio? Or would I simply say 'none?' Also, would the phenotype ratio be 1:0 or is my thinking process for this all messed up? xD

2. For the F1 generation cross there is a cross of EeWwHhCc and EeWwHhCc. I did the whole Punnett square (which, by the way, took FOREVER. D: ) but, how am I to determine the genotype and phenotype ratio of it? Also, how do I find the 'expected numbers of organisms of each type in the F2 generation?'

***I'm really sorry if I was supposed to start a new thread...I just figured it would be best to post it here, I'm not too sure how your forum rolls. o_o

*********I need this done by tonight, so any response would be greatly appreciated! Please and thankies! ;3
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Postby JackBean » Tue Apr 20, 2010 7:05 am

1. that's fairly simple, you just get one genotype (and thus one phenotype)ů

2. you have to know, which trait is dominant/recessive and which codominant ;) than just look how many of each genotype is there and group those genotypes, which have the same phenotype
http://www.biolib.cz/en/main/

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