DNA Structure and Replication

Question 1

Which direction does replication occur?

Answer 1

5’ - 3’

Question 2

what is a nucelotide made out of

Answer 2

base sugar phosphate

Question 3

what is a nucleoside made out of

Answer 3

base sugar

Question 4

what are the purine bases

Answer 4

adenine and guanine

Question 5

what are the pyramiding bases

Answer 5

thymine cytosine

Question 6

which base pairs have 2 bonds and which have 3

Answer 6

A-T have 2 bonds

C-G have 3 bonds

Question 7

what is the role of DNA helicase

Answer 7

forms replication fork by unwinding the DNA at the start of replication

Question 8

What is the role of DNA polymerase 2

Answer 8

joins nucleotides onto RNA primer

Question 9

What enzyme replaces RNA with DNA

Answer 9

DNA polymerase 1

Question 10

Which enzyme is used in prokaryotes for replication

Answer 10

DNA polymerase 3

Question 11

what is the role of DNA ligase

Answer 11

sales gaps in okazaki fragments

Question 12

what is the error rate in base pairing

Answer 12

1 in 10^9 bases

Question 13

GC to AT mutations are caused by?

Answer 13

EMS alkylates

Question 14

what is the energy driver of replication

Answer 14

pyrophosphate release

Question 15

list three key features of DNA structure

Answer 15

double stranded, antiparallel chains of nucleotides. there is complimentary base pairing - DNA is a double helix

Question 16

what is the name of the bonds that hold the backbone together

Answer 16

phosphodiester bonds between sugar phosphates

Question 17

give three differences differences between DNA, RNA structure

Answer 17

dna is double stranded
dna has deoxyribose
dna contains thymine

Question 18

what is the role of DNA primase

Answer 18

lays down a short strand of RNA to act as a primer for DNA synthesis - this is an RNA polymerase

Question 19

what do single stranded binding proteins do

Answer 19

stabilising the replication fork so that the strands don’t come back together

Question 20

what are the requirements for DNA synthesis by DNA polymerase

Answer 20

template, free 3’ OH, all four dNTP

Question 21

what are okazaki fragments

Answer 21

the short fragments of DNA synthesised on the lagging strand of DNA which contain an RNA primer - the primer is then removed by DNA polymerase 1 and the fragments are joined by DNA ligase

Question 22

in what sort of cell does a mutation have to occur in order to me inherited

Answer 22

mutation in the gametes

Question 23

what is the function of the enzyme uracil N glycosylase

Answer 23

cuts uracil from the DNA which arises from the deamination of cytosine - this can cause a C to T mutation

Question 24

what is a polymorphism

Answer 24

a sequence variation that occurs in at least 1% of the population

Question 25

what is SNP

Answer 25

single nucleotide polymorphism

Question 26

how does mature mRNA reach the cytoplasm

Answer 26

through nuclear pores

Question 27

to which end of the tRNA module is the amino acid attached

Answer 27

3’

Question 28

name three antibiotics that target prokaryotic ribosomes

Answer 28

tetracycline, streptomycin and chloramphenicol

Question 29

in which organelle does most post translational modification of secreted

Answer 29

golgi complex

Question 30

name three modifications of mRNA in eukaryotes

Answer 30

5’ cap, poly A tail, splicing out introns