Quiz 5

The enzyme telomerase uses __________________ as substrates, and ______________ as a template to synthesize the ends of eukaryotic chromosomes. RNA and deoxyribonucleoside triphosphates; RNA DNA and ribonucleoside triphosphates; RNA DNA and deoxyribonucleoside triphosphates; RNA RNA and deoxyribonucleoside triphosphates; DNA DNA and deoxyribonucleoside triphosphates; DNA

DNA and deoxyribonucleoside triphosphates; RNA

Why is uracil frequently found in human DNA? All primers are not removed from human DNA DNA polymerase III frequently uses UTP instead of dTTP as a substrate Exposure to nitrous acid leads to the deamination of Cytosine When thymine dimers are repaired, the T's are changed to U's

Exposure to nitrous acid leads to the deamination of Cytosine

Exposure of DNA to nitrous acid causes each of the following chemical reactions EXCEPT? Cytosine --> Uracil 5-Methylcytosine --> Thymine Adenine --> Hypoxanthine Guanine --> Adenine

Guanine --> Adenine

What is the principal effect of ultraviolet radiation on DNA? UV radiation causes 5-bromo-uracil to form in DNA UV radiation causes deamination of cytosine bases on the same DNA strand. UV radiation causes the formation of a dimer between adjacent thymine bases on the same DNA strand. UV radiation causes alkylation of guanine bases on the same DNA strand.

UV radiation causes the formation of a dimer between adjacent thymine bases on the same DNA strand.

Mutations in DNA may result from all of the following except: errors in transcription. physical insults on the cell, such as uv light. chemical mutagens. introduction of a base analog into DNA. spontaneous mutations due to errors in replication.

errors in transcription.

Hereditary nonpolyposis colon cancer results from defects in human proteins that are involved in which repair system? Direct repair Methyl-directed mismatch repair Base excision repair Nucleotide excision repair Recombinational repair

Methyl-directed mismatch repair

8-oxo guanine frequently base pairs with adenine when 8-oxoguanine rotates to the syn conformation. If a coding strand contains many G's, what type of mutation would occur in the genes of an organism exposed to agents that damage DNA to produce 8-oxoG lesions? G --> A mutations resulting from G:A mismatches G --> C mutations resulting from G:A mismatches G --> T mutations resulting from G:A mismatches

NOT G --> C mutations resulting from G:A mismatches

What is the role that the MutH protein plays in E. coli DNA replication? MutH encodes the 3' to 5' proofreading exonuclease of E. coli DNA polymerase III. MutH is the DNA primase MutH is an RNaseH that removes primers from the beginning of each Okazaki fragment. MutH is part of the system that corrects mismatches in DNA

NOT MutH is an RNaseH that removes primers from the beginning of each Okazaki fragment.

Nitrous acid causes damage to DNA by forming which of the following DNA adducts? pyrimidine dimers uracil 8-oxoguanine O6-methylguanine

NOT pyrimidine dimers

What is the role of the RecBCD complex in E. coli DNA metabolism? The RecBCD complex loads the beta clamp on the lagging strand at the start of each Okazaki fragment. The RecBCD complex opens the replication fork during DNA replication and binds the DnaG primase during replication. The RecBCD complex initiates repair of double strand breaks. The RecBCD complex removes uracil from damaged DNA.

The RecBCD complex initiates repair of double strand breaks.

Which of the following types of DNA damage would be most likely repaired with the nucleotide excision repair pathway? Thymine dimers 8-oxoGuanine Deaminated bases Double strand breaks

Thymine dimers

When the methyl-directed repair system detects a mismatch in dsDNA it: cannot differentiate between the template strand and the newly replicated strand. corrects the DNA strand that is methylated. corrects the mismatch by changing the base on the not-yet-methylated strand. changes the base that is methylated. none of the above

corrects the mismatch by changing the base on the not-yet-methylated strand.

When the methyl-directed repair system detects a mismatch in dsDNA it: cannot differentiate between the template strand and the newly replicated strand. corrects the DNA strand that is methylated. corrects the mismatch by changing the base on the not-yet-methylated strand. changes the base that is methylated. none of the above.

corrects the mismatch by changing the base on the not-yet-methylated strand.

Fill in the Blanks: In humans, thymine dimers are typically repaired by ___________ and deaminated bases (Ex. Uracil) are repaired using ____________. base excision repair . . . nucleotide excision repair nucleotide excision repair . . . recombinational repair nucleotide excision repair. . . base excision repair base excision repair . . . nucleotide excision repair recombinational repair . . . nucleotide excision repair

nucleotide excision repair. . . base excision repair

Xeroderma pigmentosum is linked to defects in: base-excision repair. methyl-directed repair. mismatch repair. nucleotide-excision repair. SOS repair.

nucleotide-excision repair.