A geneticist searching for mutations uses the restriction endonucleases SmaI and PvuII to search for mutations that eliminate restriction sites. SmaI will not cleave DNA with CpG methylation. It cleaves DNA at the restriction digestion sequence↓5′−CCC GGG−3′3′−GGG CCC−3′↑PvuII is not sensitive to CpG methylation. It cleaves DNA at the restriction sequence↓5′−CAG CTG−3′3′−GTC GAC−5′↑What process is the researcher intending to detect with the use of these restriction enzymes?

Ataxia telangiectasia (OMIM 208900) is a human inherited disorder characterized by poor coordination (ataxia), red marks on the face (telangiectasia), increased sensitivity to X-rays and other radiation, and an increased susceptibility to cancer. Recent studies have shown that this disorder occurs as a result of mutation of the ATM gene. Propose a mechanism for how a mutation in the ATM gene leads to the characteristics associated with the disorder. Be sure to relate the symptoms of this disorder to functions of the ATM protein. Further, explain why DNA repair mechanisms cannot correct this problem.

A geneticist searching for mutations uses the restriction endonucleases SmaI and PvuII to search for mutations that eliminate restriction sites. SmaI will not cleave DNA with CpG methylation. It cleaves DNA at the restriction digestion sequence↓5′−CCC GGG−3′3′−GGG CCC−3′↑PvuII is not sensitive to CpG methylation. It cleaves DNA at the restriction sequence↓5′−CAG CTG−3′3′−GTC GAC−5′↑Explain why CpG dinucleotides are hotspots of mutation.

A geneticist searching for mutations uses the restriction endonucleases SmaI and PvuII to search for mutations that eliminate restriction sites. SmaI will not cleave DNA with CpG methylation. It cleaves DNA at the restriction digestion sequence↓5′−CCC GGG−3′3′−GGG CCC−3′↑PvuII is not sensitive to CpG methylation. It cleaves DNA at the restriction sequence↓5′−CAG CTG−3′3′−GTC GAC−5′↑What common feature do SmaI and PvuII share that would be useful to a researcher searching for mutations that disrupt restriction digestion?

In a mouse-breeding experiment a new mutation called Dumbo is identified. A mouse with the Dumbo mutation has very large ears. It is produced by two parental mice with normal ear size. Based on this information, can you tell whether the Dumbo mutation is a regulatory mutation or a mutation of a protein-coding gene? Why or why not?

Considering the Dumbo mutation in Problem 37, what kinds of additional evidence would help you determine whether Dumbo is a mutation of a regulatory sequence or of a protein-coding gene?

Thinking back to the discussion of gain-of-function and loss-of-function mutations in Section 4.1, and putting those concepts together with the discussion of base substitution mutations in this chapter, explain why gain-of-function mutations are often dominant and why loss-of-function mutations are often recessive. Give an example of a type of gain-of-function mutation that is dominant and of a loss-of-function mutation that is recessive.