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Q: Mendelian law and Punnett squares. ( Answered ,   0 Comments )
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 Subject: Mendelian law and Punnett squares. Category: Science > Biology Asked by: newcomer-ga List Price: \$10.00 Posted: 30 Sep 2005 12:17 PDT Expires: 30 Oct 2005 11:17 PST Question ID: 574713
 ```Brachydactyly, inherited as a dominant trait, is a skeletal abnormality resulting in unusually short fingers. A brachydactylous woman(heterozygous) mates with a normal man. Could they have brachydactylous children? What proportion of the children would be expected to have the trait? Show progression of answer through use of Punnett square.```
 ```Hi newcomer-ga, and welcome back to Google Answers. First, let's assign letters to the brachydactyly gene alleles. Let "B" be the dominant allele and "b" be the recessive (normal) allele. Each person has two alleles for any given gene. For the woman, she is Bb, meaning that she has one dominant (B) allele and one recessive normal (b) allele. She mates with a normal man. Because the brachydactyly gene is dominant, a normal person (male or female) must not have a (B), or they would have brachydactyly. So, the male must be (bb). Now, we use the Punnett square (with the alleles donated by the male on top and those from the female vertically) to figure out what genotypes the offspring will have: b b ----------- B | Bb Bb b | bb bb So, we get 2 offspring that are (Bb) and 2 that are (bb). Put another way, 50% are (Bb) and have brachydactyly. The remaining 50% are (bb) and are normal. You can read more about Punnett squares, their use, and their interpretation at Wikipedia: http://en.wikipedia.org/wiki/Punnett_Square I hope this answer was helpful. Best of luck in your studies. Feel free to request clarification. -welte-ga```
 newcomer-ga rated this answer: `Very nice, I have another question coming at you that is a bit more involved.`