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all about punnett squares

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

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Postby uchiha_sasuke » Sat Feb 04, 2006 9:35 am

another question. how do i solve this problem:
a cross of F1 plants heterozygous for height should produce a ratio of tall to short plants of 3:1. Three seeds from such a cross have been grown and they ahave produced three tall plants. what are the chances that a fourth seed will produce a short plant? And what do you mean by probability?
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Postby Poison » Sat Feb 04, 2006 5:10 pm

Have you made apunnet square? Try it. Then think that tall is dominant over short ( you can understand this (even if you don't know) from the ratio given. Make the punnet square you will findand understand.)
For probability: Lets say you made a punnet square and crossed. You think the whole as 100. then you divide the whole into percentage (%).
And a hint for you: pay attention to the ratio and the words "heterozygote F1". :)
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Help!?!?

Postby uchiha_sasuke » Mon Feb 06, 2006 9:41 am

oh. now i understand. though i haven't actually done the punnet square yet because i'm quite confused with the question, i understand your point. but now, my question is what's a dichotomous / branching method? is there really a trihybrid cross because all i know are mono and dihybrid cross. i've never heard of it, sorry. could you explain it please?! :?
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Postby uchiha_sasuke » Thu Mar 02, 2006 11:15 am

how do you solve this kind of problem? I never seem to have any idea on how to answer this. i even have no idea on how to make a punnet square on this problem. help me. onegai!

A normal visioned and bald woman whose father is bald and a mother who is red-green color blind marries a man who is nonbald but is red-green color blind.

a. What could be the probability that their children will be:
1. bald girls?
2. red-green color blind boys?
3. bald boys?
4. normal visioned girls?
5. nonbald and normal visioned girls and boys?
6. red-green color blind and bald boys and girls?
7. nonbald and red-green color blind boys and girls?
8. normal visioned and bald boys and girls?
b. Give the phenotypic ratio and genotypic ratio.
c. What could be the probability that they're children will be both normal to girls (in percent)?

please help me! i really have no idea on how to solve this!
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