A dominant mutation of the MCMB gene (L) causes lactase causes lactase productio

Question

A dominant mutation of the MCMB gene (L) causes lactase causes lactase production to occur in adult humans leading to the persistence of the ability to digest lactose in many adults. In this case, we see an example of a mutation with a beneficial effect (an ability to consume dairy products). The mutation frequency for lactase persistence is not equal in all populations: some regional populations have higher rates of adults that are able to digest lactose lactase than others. For example, might lactase persistence be a favorable adaptation in one population, but have little significance in another? Historically, European populations relied more heavily on dairy products like milk and cheese, while these products were less important in Asian populations. This suggests the mutation that leads to lactase persistence would be more prevalent (evolve towards a higher frequency) in populations that consume more dairy products, as it is an advantageous adaptation. Lactose metabolism is also an example of a trait that exhibits phenotypic plasticity. This means the same the same genotype may produce different phenotypes depending on the environmental conditions. If an adult is lactose intolerant (II), the severity of t he symptoms they experience depends on how they interact with their environment. For instance, they can avoid feeling ill by choosing not to consume dairy products, or they can choose to take supplements that provide the missing lactase enzyme to aid in digestion and reduce illness associated with lactose intolerance. Lactose mutation inheritance activity: Suppose a woman without lactase persistence (the non-mutant recessive phenotype) wants to have a child with a man who is heterozygous for the lactase persistence mutation, L. Fill in parents and offspring genotypes in a Punnett square to simulate the potential genotypes of the couples' offspring. Remember, this condition is not sex linked (the X and Y chromosomes are not involved). 1. What is the probability that their child will have lactase persistence (dominant mutant phenotype)? 2. If they have a second child, what is the probability that child will have lactase persistence? If the father in the above cross were instead homozygous for the lactase-persistence mutation, could any of their offspring not have lactase persistence? Diagram a Punnett square using this male homozygous genotype to support your answer.

Explanation / Answer

Woman is without lactase persistence (ll). Man is heterozygous for the lactase peristence mutation (Ll). The mating between these two is described in the following Punnett square,

1) The probability that their child will have lactase peristence is 1/2 (0.5).

2) The probability that their second child will have lactase peristence is also 1/2 (0.5).

L l l Ll ll l Ll ll

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.