DNA Structure and Replication

Question 1

Purines

Answer 1

double ring: adenine and guanine

Question 2

pyrimidines

Answer 2

single ring: thymine (uracil) and cytosine

Question 3

DNA

Answer 3

nucleotides joined by covalent bonds between 3’ OH group and 5’phosphate to make sugar phosphate backbone

A–T, C—G

Question 4

DNA Replication Enzymes

Answer 4

helicase: unzips helix
topoisomerase: relaxes ahead of replication fork (DNA gyrase) Type I: cuts one strand then seals, Type II: cuts both strands then seals
single stranded binding proteins:
polymerases: DNA Pol III begins synthesis at primer, proofreading; Pol I excises primer (5’to3’), fills gaps in lagging strand
Primase (RNA polymerase)
ligases: seals fragments

Question 5

Werner syndrome, Diskeratosis congenita

Answer 5

problem with telomere replication

Question 6

Mutations in DNA

Answer 6

silent: codes for same AA
missense: changed AA
nonsense: stop codon
frameshift: insertion or deletion

Question 7

Single Nucleotide Polymorphisms (SNPs)

Answer 7

change in a base pair, can influence how we respond to stress and disease

Question 8

Telomerase

Answer 8

telomere has G repeated sequence, RNA part of telomerase pairs and adds nucleotides, replaces RNA template with DNA, telomerase leaves