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