DNA and DNA repair

Question 1

what is a autocatalytic reaction

Answer 1

where a product itself acts as a catalyst for the reaction

Question 2

what is a central dogma process

Answer 2

process by which the instructions in DNA are converted into a functional product

Question 3

explain the structure of DNA

Answer 3

• deoxynucleotides consist of sugar, phosphate and base
• nucleotides form a sugar-phosphate backbone
• two complementary anti-parallel DNA strand pair to form double strand DNA
• DNA is twisted in a double helix

Question 4

what are the DNA base

Answer 4

Purines:

• Adenine
• Guanine

Pyrimidines:

• Thymine
• Cytosine

Question 5

what kind of replication does DNA have

Answer 5

semiconservative

Question 6

what is the difference of leading strand and lagging strand?

Answer 6

leading strand

• requires only one primers
• follows the replication fork
• continuous

lagging strand

• require multiple primers
• replicates opposite direction of the replication fork
• discontinuous

Question 7

mechanisms of lagging strand

Answer 7

• new RNA primer synthesis by DNA primase
• DNA polymerase adds to new RNA primer to start new Okazaki fragment
• DNA polymerase finishes
• old RNA primer erased and replaced by DNA
• Okazaki fragment join and sealing by DNA ligase

Question 8

what is telomerase

Answer 8

an enzyme made of protein and RNA subunits that elongates chromosomes

Question 9

problem with lagging strand replicating the end of a eukaryotic chromosome

Answer 9

can’t replicate it till the end, no place for RNA primer

Question 10

what can be used to replicate the end telomer of a eukaryotic chromosome in lagging strand

Answer 10

terlomerase

Question 11

mechanism of telomere replication

Answer 11

telomerase binds to the parent strand
to give an extension of fo the 3’ end
DNA polymerase finishes off the last DNA synthesis section

Question 12

benefit of shortening of telomeres

Answer 12

limits cell proliferation and induces senescence

Question 13

what are the common replication errors

Answer 13

polymerase proofreading

mismatch repair

Question 14

DNA are subject to what damage and give examples

Answer 14

spontaneous damage

• mis-incroporation during DNA replication
• chemical deay of DNA (hydrolysis)

Induced damage

• endogenous agents (hydrolysis, oxygen radicals)
• exogenous agents (lonising radiation, UV-light, cancer therapeutic drugs)

Question 15

consequences of DNA damage

Answer 15

Mutations

blockage of replication/transcription

cell death

cancer

organism death

Question 16

2 main group of repair pathway

Answer 16

excision repair

double strand break repair

Question 17

common stopes in DNA repair

Answer 17

recognition of the damage
removal of the damage
fill in the gap (DNA synthesis)
ligate the newly synthesized DNA to ‘old’ strand

Question 18

what is used to catalyse during the stand invasion?

Answer 18

RecA

Question 19

what is deamination

Answer 19

removal of amino group

Question 20

aim of stand invasion

Answer 20

act as a primer and copy the strand from the DNA

and IT HAS TO BE IN THE 3’ ENDS

Question 21

aim of stand invasion

Answer 21

act as a primer and copy the strand from the DNA

and IT HAS TO BE IN THE 3’ ENDS

Question 22

WHAT SI BASE EXCISION REPAIR

Answer 22

it corrects DNA damage from oxidation, deamination and alkylation

Question 23

what is homologous recombination

Answer 23

a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA