Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry > DNA Replication And Repair > Flashcards

DNA Replication And Repair Flashcards

1
Q

by convention the base sequence of nucleic acid strand is written as

A

5’ to 3’(if not mentioned, it means its from 5’)

if from 3’ to 5’ it should be mentioned in the sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

m

A

m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

chargaff rule

A

no. of purines= no.of pyrimidines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

B DNA

A

watson crick model

right handed double helical structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

which bonds are broken during denaturation

A

H bonds only leading to ssDNA

NOT covalent(including phosphodiesterase bonds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is positive and negative supercoiling

A

POSITIVE
if the DNA wound more loosely than the WC dna

NRGATIVE
if the DNA wound more tightly than the watson crick dna.
req for most biologic reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

fxn of topoisomerases

A

change the amount of supercoiling in dna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

basic packing unit of chromatin

A

nucleosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

heterochromatin

A

tightly condensed

areas of chromosomes not expressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

nucleosome(10 nm chromatin) is made up of

A
  1. DNA
  2. two copies of each of the following histones
H2A
H2B
H3
H4
forming histone octamer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

where is H1 located and its fxn

A

ass with linker DNA bw nucleosomes

helps in further packing to solenoid like structure(30nm fibre)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how many origin of replication are there in prokaryotic dna

A

only 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

replication is bidirectional

A

true

at a Origin of replication 2 replication forks are created that move in opposite direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

dna pol has proof reading activity whereas rna pol does not

A

yes

3’ to 5 ‘ exonuclease proof reading activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

dna pol requires a primer but rna pol does not?

A

true

dna pol can not initiate strand synthesis.

they can only extend the strand from 3’ end of primer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

role of dna pol I in prokaryotes

A

removes primer (as in okazaki fragments) due to 5’ exonuclease activity and synthseise new dna from 3’ end of neighbouring okazaki fragments.

the fragments are sealed by dna ligase

17
Q

drugs acting on bacterial and human topoisomerases

A

quinolones

etoposide, teniposide

18
Q

unwinding of the dna done by

A

helicase

break the double stranded dna i.e. H bonds

19
Q

quinòlones target

A

topoisomerase II/ DNA gyrase

resp for negative supercoiling

20
Q

whatvare the different eukaryotic dna pol

A

alpha, delta- dna synthisis

gamma-mitichondrial dna syn

beta, epsilon-dna repair

21
Q

dna syn in prokaryotes by

A

dna pol III

22
Q

removal of the rna primers by

A

eukar- RNAHase

prokar- DNA pol I

both have 5’to 3’ exonuclease activity

23
Q

replacement of rna with dna in primer during replication by

A

eukar-DNA pol delta

prokar- DNA pol I

24
Q

okazaki fragments are joined via

A

dna ligase in both eu/prokaryotes

25
Q

moa of AZT

A

thymidine analog

enters cell and converted to triphosphate

DNA pol(of RTase of virus) adds it to the dna chain

since no OH’ group in the 3’ position.

therefore chain termination.

26
Q

proteins inbolved in the regulation of G1 checkpoint

A
  1. cyclinD , Cdk4(cyclin dep kinase)
  2. RB
  3. p53
27
Q

role of cycin D and Cdk4

A

cyclin D binds to Cdk4 and makes the cell to enter from G1 to S phase

Cdk4 phosphorylates RB which releases the captured EF2 required for replication

28
Q

role of p53

A
  1. provides time for cell to repair the damage by arresting it in G1 phase

p53 inhibits Cdk4 which ll not be able to inactivate RB

2.if excess damge then apoptosis of cell

decrease in growth promoting gene and BCL2 (antiapotosis)

29
Q

gene inactivated in Telengia ectasia

A

ATM

encodes a protein kinase essential for p53 activity

30
Q

defect in xeroderma pigmentosa

A

thymine dimers formed due to UV radiation are not corrected due to def in exi/endonuclease enz

dimers interfere with DNA replication and gene expression.

31
Q

defect in HNPCC

A

mutation in one of the 2 genes– hMSH2/ hMLH1 leads to defective repair of DNA mismatches formed after DNA replication

32
Q

features of xeroderma pigmentosum

A

extreme uv sensitivity

excessive frekling

multiple skin cancers

corneal ulveration

33
Q

cytosine deamination defect

A

cytosine converted to uracil in DNA

recognised and removed by uracil glycosylase enzyme.

dna pol fills gap

dna ligase seals the repaired dna to original strand

34
Q

microsatellites

A

these are di, tri and tetranucleotide repeats dispersed in dna usually in the noncoding region.

if the cell lack mismatch repair then the replicated dna ll vary in the no. of repeats in that locus.This variation is called microsatellite instability.

eg: found in tumor cells of HNPCC

35
Q

most abundant rna in the cell

A

ribosomal RNA

2nd most abundant :tRNA

36
Q

hnRNA represents(heterogenous nuclear)

A

precursor mRNA/pre mRNA

after posttranscriptional processing of it mRNA is formed

37
Q

which rna participates in mRNA splicing/removing of introns

A

snRNA

small nuclear

Biochemistry (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions