Below is a pedigree (Figure 5) illustrating the inheritance pattern of lactase p

Question

Below is a pedigree (Figure 5) illustrating the inheritance pattern of lactase persistence phenotype in a hypothetical family. Each shape represents a family member and tells us formation about their phenotypes. We can use the information for multiple family members to infer more specific information about other individuals, such as their genotype. 1. What is the mode of inheritance for lactase persistence: dominant or recessive? How does the pedigree support this conclusion? 2. If male III-1 married a female without lactase persistence (no-mutant phenotype), could they produce children with lactase persistence (mutant phenotype) and does the sex of the child make a difference? Use a Punnett square to explain your answer. Making Connections: Draw a pedigree for Molly and Ryan's family (using the genotypes you discovered in Part 1 of this lab) to demonstrate the inheritance pattern of DMD within this family. Group Activity-Interpreting a Pedigree: You and your table group are genetic counselors. A family has come to you because they want to better understand how a disorder has spread through their family. As a group, use your knowledge from the previous pedigree examples to determine what mode of inheritance this disorder represents (autosomal dominant or recessive, or sex-linked recessive), and make a case for why you decided on this type of inheritance. What would you tell the family about the nature of this disorder? Each table will share their conclusions with the class.

Explanation / Answer

1. The mode of inheritance of lactase persistence appears to be dominant, as the presence of just one allele is enough to produce an affected phenotype. Additionally, one can see from the pedigree, that pairing between affected male II-1, and unaffected female II-2 gives rise to both affected and unaffected males among the children, which shows that the trait is not X-linked, but autosomal.

2. We have already established that the pattern is autosomal dominant. Now, let us assume the gentype of male III-1 to be LL, where L is the wild type allele for lactase persistence. The genotype of the unaffected female would also be LL.  Thus, using a Punett square, we get

.Thus, all the offspring have the LL genotype, which means this cross will not produce any affected offspring. Also, as the trait is autosomal, sex of the offspring will not make any difference.

FemaleMale L L L LL LL L LL LL

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