DNA replication

Question 1

Semiconservative model of DNA replication

Answer 1

Parental molecule, separation of parental strands into template strands (h bonds), formation of new strands complementary to template strands (h bonds)

Question 2

Chromosomes

Answer 2

Linear and circular; type of DNA is replicated

Question 3

E coli vs human cell

Answer 3

E coli: single circular chromosomes; about 4k genes
Human cells: linear chomosomes; about 23k gens

Question 4

DNA replication

Answer 4

DNA synthesis

Question 5

Origin of Replication

Answer 5

Site where replication of DNA begins; specific sequence of nucelotides; site where parental strands separate and form bubble with two forks

Question 6

Replication fork

Answer 6

Y-shaped region on a replicating DNA molecule where parental strands are unwound and new strands are synthesized

Question 7

Helicase

Answer 7

Enzyme that untwist or unzips DNA; double helix at replication forks; separating them to make them available as template strands

Question 8

Single strand binding proteins

Answer 8

protein that binds to unpaired DNA strands during replication, stabilizing them and holding them apart while they serve of templates for synthesis of complementary strands of DNA

Question 9

Topoisomerase

Answer 9

protein that breaks, swivels, and rejoins DNA strands; relieves strain of double helix ahead of replication forks

Question 10

Primase

Answer 10

Synthesizes RNA primers, using parental DNA as template

Question 11

Primer

Answer 11

short polynucleotide with a free 3’ end, bound by complementary base pairing to template strand and elongated with DNA nucleotides during DNA replication

Question 12

DNA polymerase

Answer 12

catalyze elongation of new DNA strands by addition of new nucleotides to 3’ end; many different types

Question 13

DNA polymerase only adds nucleotides only to which end?

Answer 13

3’ end of growing strand

Question 14

New DNA strand can only elongate in which direction?

Answer 14

5’ to 3’

Question 15

Leading strand

Answer 15

new complementary DNA strand synthesized continuously along the template strand toward replication fork in 5’ to 3’ direction

Question 16

How many primers are needed for DNA polymerase III to synthesize leading strand?

Answer 16

Just one

Question 17

Lagging strand

Answer 17

Discontinuously synthesized DNA strand; elongates by means of Okasaki fragments; synthesized in 5’ to 3’ direction away from replication fork

Question 18

Okazaki Fragments

Answer 18

short segment of DNA synthesized away from replication fork on a template strand during DNA replication; joined together to make up lagging strand of newly synthesized DNA

Question 19

DNA ligase

Answer 19

linking enzyme for DNA replication; catalyze covalent bonding of 3’ end of one DNA fragment to 5’ end of another

Question 20

Steps of synthesis of lagging strand

Answer 20

1. Primase makes RNA primer
2. DNA polymerase III makes Okazaki fragment
3. DNA pol III detaches
4. Fragment two is primed
5. DNA pol 1 replaces RNA with DNA
6. DNA ligase forms bonds between DNA fragments
7. the lagging strand is complete

Question 21

DNA polymerase 1

Answer 21

Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides added to 3’ end of adjacent fragment

Question 22

DNA polymerase III

Answer 22

Using parental DNA as template, synthesizes new DNA strand by adding nucleotides to RNA primer or pre-existing DNA strand