Campbell Biology (11th Edition)

Published by Pearson
ISBN 10: 0-13409-341-0
ISBN 13: 978-0-13409-341-3

Chapter 14 - 14.4 - Concept Check - Page 290: 3


Using P for the allele for polydactyly and p for the allele for the normal number of digits. Since Joan's mom has polydactyly, but only some of her children got this dominant allele, Joan's mom is Pp. Her unaffected father must be pp since not all of the children have the trait. That makes the cross between her parents ppxPp, and Joan could only have one copy of the P allele, making her Pp.

Work Step by Step

This is asking you to do pedigree analysis on Joan's family. Pay special attention to the dominant nature of polydactyly to see that her father must be homozygous recessive (as it's the only way he would not exhibit polydactylism) and that her mother must be a heterozygote for any siblings to also be unaffected/have a pp genotype. Then you can see that Joan, who must be NN or Nn to have the trait, could not be NN from these parents, making her Nn.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.