Paul Andersen introduces the Punnett Square as a a powerful tool in genetic analysis. He tries to address major misconceptions that students have when use a Punnett Square. He gives a number of examples of monohybrid crosses and one example of a dihybrid cross. The square is a simple tool that uses the outcome of meiosis to determine possible offspring in a cross.
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Link to sound: http://www.freesound.org/people/CosmicD/sounds/72556/
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Hey super helpful for my test tomorrow! So if anyone here who's good at this stuff reads this could you just confirm my answer for the question he leaves us with? Thanks! So I'm assuming the answer here is the Punnett square would be 4 by 1, because for the RrYy each character there are two possible alleles and 2x2 is 4 possibilities, but for the rryy, it could only give an rr and a yy and nothing else so the only possibility that parent could give is rryy.
Also just to make sure I really got this down I'll go a step further - if you were to complete the Punnett Square, you would have one RrYy (heterozygous dominant for both), one Rryy (heterozygous for the first, homozygous recessive for second), one rrYy (homozygous recessive for the first, heterozygous for second), and one rryy (homozygous recessive for both). So there would be a 1:1:1:1 ratio for this dihybrid cross. And nowhere will you be seeing homozygous dominant for either trait because at least one recessive allele will always be contributed if I'm correct.
Thank you again and please let me know what I did right/wrong, and correct me if I'm wrong anywhere!
"And this one right here, it's gonna be round, and it's gonna be yellow, so it's gonna be round and yellow, and this one you can see, it's gonna be round and yellow, and round and yellow, and round and yellow, and round and yellow, and round and yellow, and round and yellow, and round and yellow, and round and yellow. So in other words, nine are going to be round and yellow."
THANK YOU SO MUCH FOR DOING THIS!! YOU EXPLAIN IT MUCH BETTER THAN MY TEACHER DOES AND NOW I FINALLY UNDERSTAND THE DIHYBRID CROSSES!! I have a test about it tommorrow but now I don't have a bad feeling anymore! Thanks a bunch!
Mr. Anderson I am quite confused regarding what is trait and an allele. In case of sex linked inheritance we have the recessive Gene of haemophilia or any other disease on the x chromosome which leads to the appearance of a trait. So what is the relation between the gene, the allele and the trait in this case.
I am an older student in an art major curriculum retaking biology because... not really sure. Maybe the school thought it might help me mix egg tempura colors. It's been a running firefight to maintain the grade average I need and more of a challenge than I thought I'd have. But I just want to say that quite a few of the cell division, reproduction and genetic topics were so much easier coming from your videos than the McGraw Hill textbook. You've got a real gift for instruction.
Owe you big time and thanks.
It does occur, if say frequency of defective allele on X chromosome in a gene pool would be 0.01 than 0.01 males would be affected, as for the females 0.01 x 0.01 = 0.0001 would be affected - in females we would see that color blindness will occur 100 times less frequent than in males.
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