DNA replication (younger)

Question 1

DNA replication is ____________ and _____________.

Answer 1

Bidirectional and semiconservative

Question 2

Replication begins in the interior of a DNA molecule and proceeds in both directions.

Answer 2

Bidirectional

Question 3

Each copy of the DNA molecule, after replication, contains one strand from the original template and one newly synthesized strand.

Answer 3

Semiconservative

Question 4

What is the difference betweeen Eukaryotic and Prokaryotic DNA

Answer 4

Pro- one origin of replication, circular DNA

Euk- multiple origins of replication, to replicate in a reasonable amount of time

Question 5

What proteins bind to the single strands and prevent reannealing and protect DNA from nuclease degradation.

Answer 5

Single stranded binding proteins (SSBs)

Question 6

What enzyme forms the replication fork by unwinding the DNA double helix?

Answer 6

DNA helicase

Question 7

What enzyme removes the supercoiling by cutting one strand which allows the DNA to swivel around the intact strand, then seals the nicked strand.

Answer 7

Type I topoisomerase

Question 8

What enzyme cuts both strands to relieve supercoiling, then re-ligates the two strands.

Answer 8

Type II topoisomerase

Question 9

What enzyme is a type of Topoisomerase II that introduces (-) supercoils that are inhibited by quinolone drugs?

Answer 9

DNA gyrase

Question 10

You can’t package DNA without this enzyme.

Answer 10

DNA gyrase

Question 11

SInce DNA is antiparallel, the template must be read __ to __.

Answer 11

3’ to 5’

Question 12

Nucleic acid synthesis is __ to __ and template reading is __ to __.

Answer 12

5’ to 3’

3’ to 5’

Question 13

How is the other strand synthesized in DNA replication?

Answer 13

the other strand (the lagging strand) is synthesized discontinously… as replication fork advances, small fragments of DNA are synthesized 5’ to 3’ away from the replication fork

Question 14

What are the discontinuously synthesized fragments called?

Answer 14

Okazaki fragments

Question 15

_____ is an RNA polymerase that copies the first ~10 nucleotides to “prime” synthesis.

Answer 15

Primase

Question 16

DNA polymerases require a free ______ group to begin synthesis. This problem is solved by the action of ______.

Answer 16

3’ OH

Primase

Question 17

_________ is further cleaved to inorganic phosphate (Pi) to make the reaction irreversible, and drive the reaction in the forward direction.

Answer 17

Pyrophosphate

Question 18

The enzyme in prokaryotes that elongates both the leading and lagging strands.

Answer 18

DNA polymerase III

Question 19

3’ to 5’ exonuclease activity… Pol III checks each added nucleotide to make sure it is correctly base-paired with the template strand. This activity is called what?

Answer 19

Proofreading

Question 20

What enzyme has has 5’ to 3’ and 3’ to 5’ exonuclease activity and removes RNA primer with dNTPS. (rNTPs with dNTPs)

Answer 20

Pol I

Question 21

What enzyme seals the nick that remains after the RNA primer is removed and replaced with dNTPs?

Answer 21

DNA ligase

Question 22

DNA replication steps»> what are they briefly?

Answer 22

Strand seperation (DnaA protein)
Prevent reannealing (SSB proteins)
Unwinding of DNA (Helicase)
RElieves supercoiling (Topoisomerase)
Leading and Lagging strands synthesized
RNA primer laid down to begin new strand (Primase)
Extension of leading and lagging strand (Pol III)
Removal of RNA primers and replaced with DNA (Pol I)
Nick sealed in the fragments (DNA ligase)

Question 23

Leading strand synthesized __________, lagging strand synthesized _________.

Answer 23

Continuously

Discontinuously

Question 24

_________ contains primase + DNA polymerase (begins strand synthesis)

Answer 24

Pol æ (Alpha)

Question 25

_________is a Dna polymerase + proofreading (extends strands)

Answer 25

Pol D (Delta)

Question 26

What adds nucleotides to extend the 3' end of the DNA to help line up the strands.

Answer 26

Telomerase

Question 27

What is an aspect of aging of a cell? What protects DNA on the ends?

Answer 27

Telomeres

Question 28

Certain polymerases can copy RNA into DNA... What are 3 things that have this reverse transcription?

Answer 28

Reverse Transcriptase RNA-dependent DNA polymerase Telomerase

Question 29

_____________ is a common strategy in many viruses like HIV because it lacks proofreading activity and there is high mutation rate.

Answer 29

Reverse transcriptase

Question 30

A defect in mismatch repair is responsible for _____________________, one of the most common inherited cancers.

Answer 30

Hereditary nonpolyposis colorectal cancer (HNPCC)

Question 31

Mutations can be caused by what other 4 things other than replication errors?

Answer 31

Spontaneous mutations Exposure to chemicals Radiation UV light- (causes pyrimidine dimers instead of normal thymine dimers)

Question 32

What enzyme does most of DNA repair?

Answer 32

Pol I in prokaryotes

Question 33

What is a rare genetic disorder that results from a deficiency in excision endonuclease?

Answer 33

xeroderma pigmentosum