Chapter 19 Gene Mutation and DNA Repair

MutL

Acts as a linker that helps loop the DNA

Which of the following are examples of base pair mismatches? Select all that apply

Adenine on parent strand and Cytosine on daughter strand Cytosine on parent strand and Adenine on daughter strand Cytosine on parent strand and Thymine on daughter strand

Which of these represents the correct order of steps during a typical DNA repair system?

Detection → Removal → Replication

Nucleotide excision repair (NER) is the main system used in the repair of

bulky, helix distorting lesions.

MutS

detects the mismatch

Alkylating agents cause mutations by

disrupting the normal pairing between nucleotides within the DNA.

A position effect can alter gene expression in cases when the gene is moved from a less condensed, or ______ chromosome, where it is active, to a very highly condensed, or ______ chromosome, where its expression may be turned off.

euchromatic ; heterochromatic

Exonuclease

Digests the nonmethylated strand

MutH

Makes a cut in a nonmethylated strand

In the mismatch repair system, the proteins ______ form a complex that activates _____, which is already bound to a ______ DNA site.

MutS/MutL ; MutH ; hemimethylated

MutU

Separates strands at the cleavage site

Which of these tests is used to evaluate the mutagenicity of an agent?

The Ames test

True or false: Most DNA repair systems involve three major steps: detection of the error, removal of the abnormality, and its replacement with normal DNA.

True

A mutation in a gene that causes an amino acid change in the encoded protein is called a

missense mutation.

Errors in DNA replication are examples of ______ mutations, while mutations caused by ultraviolet light are ______ mutations

spontaneous; induced

Translesion synthesis refers to

the replication of a template strand that contains DNA damage.