In the film, geneticists discovered that the difference between lactase-persistent (lactose-tolerant) and lactase-nonpersistent (lactose-intolerant) people was due to a mutation. This mutation was not in the part of the lactase gene that encoded the lactase enzyme. In which of the following was the mutation located? 1. an intron of the lactase gene 2. the gene for glucose production 3. different genes for different individuals 4. the genetic switch for the lactase gene
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Step 1: The mutation that causes the difference between lactase-persistent and lactase-nonpersistent individuals was not in the part of the lactase gene that encodes the lactase enzyme. Show more…
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The ability of adults to tolerate milk, cheese, and other lactose-containing dairy products co-evolved with dairy farming in Central Europe about 7,500 years ago. To tolerate lactose (the sugar present in milk and derivates, an individual must express lactase (the enzyme that breaks lactose into glucose and galactose. Among persons of European descent, lactose tolerance is strongly associated with a C to T substitution at a polymorphic site 13,910 bp upstream of the lactase gene. This mutation results in the persistent expression of lactase into adulthood enabling individuals carrying a T-13,910 allele to digest lactose as adults Based on the position of the mutation, it is probably located at: an insulator the regulatory promoter the core promoter an enhancer
Maitreya E.
You are studying the properties of a new kind of regulatory mutation of the lactose operon. This mutation, called $S$, leads to the complete repression of the $\operatorname{lac} Z$, lacY, and lacA genes, regardless of whether inducer (lactose) is present. The results of studies of this mutation in partial diploids demonstrate that this mutation is completely dominant over wild type. When you treat bacteria of the $S$ mutant strain with a mutagen and select for mutant bacteria that can express the enzymes encoded by $\operatorname{lacZ}, \operatorname{lac} Y$, and $\operatorname{lacA}$ genes in the presence of lactose, some of the mutations map to the lac operator region and others to the lac repressor gene. On the basis of your knowledge of the lactose operon, provide a molecular genetic explanation for all these properties of the $S$ mutation. Include an explanation of the constitutive nature of the "reverse mutations."
Jennifer S.
Madhur L.
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