Chapter 18 Quiz

characteristics of transposable elements

- able to insert at many different locations throughout a genome - short flanking direct repeats present on both side of a transposon - staggered breaks made in the target DNA during insertion - can take place through a DNA intermediate in some cases

facts about mutations

- mutations can be used to examine biological processes - somatic mutations are numerous, occurring at a rate one per every million cell division - mutations are a source of all genetic variation - gene mutations affect single gene, whereas chromosome mutations affect the number or structure of chromosomes

examples of a DNA repair mechanism

- nucleotide-excision repair - mismatch repair - direct repair - base-excision repair

What is a conditional mutation?

a mutation that affects the phenotype only under certain conditions

What is a missense mutation?

a mutation that results in a different amino acid in a protein

What is the Ames test?

a test to screen for mutagenic chemicals

What is an example of a transversion mutation?

adenine is replaced by thymine

Which mutagens incorporate into DNA and frequently pair with the wrong base?

base analogs

Which statements about mutations is incorrect?

germ line and somatic mutations are both passed on to offspring

Which of the examples listed is NOT a DNA repair mechanism?

insertion sequence repair

How does direct repair return DNA errors to their original sequences?

it removes functional groups or bonds from the altered nucleotide to restore the original structure

How do mismatch repair enzymes in E. coli differentiate between the old and new strands of DNA?

methylation of the adenine in the GATC sequence of the old strand

What is an environmental agent that significantly increases the rate of mutation above the spontaneous called?

mutagen

NOT a characteristic of transposable elements

only found in plants

What changes does UV light produce in DNA molecules?

pyrimidine dimers

How does transposition cause mutations?

transposable elements can insert themselves into other genes and disrupt their function

Barbara McClintock is known for her discovery of

transposons

What disease occurs as a result of mutations in the genes for DNA repair systems?

xeroderma pigmentosum