L16A+B DNA Replication

Question 1

What is meant by replication

Answer 1

Process where DNA makes a copy of itself each time the cell divides
Occurs in S phase of interphase

Question 2

Rules of DNA replication

Answer 2

Semi conservative
Begins at multiple origins and proceeds bidirectionally
Exhibits polarity(proceeds in a 5’to3’ direction
Very accurate

Question 3

How far are origins spaced

Answer 3

30,000 to 300,000 base pairs apart

Question 4

How are origins identified

Answer 4

By origin recognition complex proteins

ORC

Question 5

What are steps of DNA replication

Answer 5

1-DNA unwinding
2-DNA primer synthesis
3-DNA polymerization
4-degrading RNA primers
5-Ligation

Question 6

Enzyme that breaks down bonds between nit bases

Answer 6

Helicase

Question 7

What prevents unwound DNA from rewinding back

Answer 7

Single stranded DNA binding proteins

Question 8

What prevents super coiling of DNA

Answer 8

DNA topoisomerases

Question 9

Unwinding of DNA causes formation of structure called…

Answer 9

Replication fork

Question 10

Enzyme responsible for replication

Answer 10

DNA polymerase

Question 11

What does DNA polymerase require to work

Answer 11

RNA primer

Question 12

How are RNA primers synthesized

Answer 12

By RNA primase

Question 13

Leading strand

Answer 13

5’»»3’ continuously away from origin

Question 14

Lagging strand

Answer 14

5’> 3’ towards the origin

Question 15

What are Okazaki fragments

Answer 15

Short fragments of DNA that are appx 150 base pairs long

Question 16

Types of DNA polymerases

Answer 16

DNA poly a priming and initial synthesis 
DNA poly B DNA repair
DNA poly y mtdna replication 
DNA poly delta lagging strand synthesis
DNA poly E leading strand synthesis

Question 17

How are RNA primers removed

Answer 17

5’»»>3’ exonuclease

And gap filled by DNA polymerase

Question 18

What is ligation

Answer 18

Creation of phosphodiester bond between individual DNA fragments so that whole strand becomes one continuous strand
Enzyme: DNA ligase

Question 19

How do diff steps of replication target anti cancer and anti microbial agents

Answer 19

1.incorporate DNA to interfere with chain elongation and induce defective ligation of newly synthesized DNA (antiviral: acyclovir against herpes)
2-inhibit topoisomerase in cancer cells and in bacterial cells(quinolone antibiotics)

Question 20

What is proof reading

Answer 20

Process in which there is a cont check on newly inserted nucleotides
Base pair mismatch occurs at a freq of 1 per 10,000 nucleotides

Question 21

What enzymes proof read

Answer 21

DNA poly 1 and 3

Question 22

Function of telomeres

Answer 22

Maintain structural integrity of chromosome and prevent attack by nucleases and allow repair systems to distinguish a true end from a break in dsDNA

Question 23

Non coding hexameric sequence is..

Answer 23

AGGGTT

Question 24

What is telomerase

Answer 24

Complex contains a protein that acts as a reverse transcriptase and a short RNA template to synthesize tandemly repeating base sequences

Question 25

How can HIV and COVID replicate inside body

Answer 25

They have reverse transcriptase which they use inside the human body to reversely transcribe the RNA (in their cells) to DNA and start replication