DNA

Question 1

Nucleotides

Answer 1

composes each strands. made of a base (A,T,G,C), sugar and phosphate.

Question 2

The bases

Answer 2

Adenine (A) bonds with Thymine (T) for DNA and Uracil (U) in RNA. Cytosine (C) bonds with Guanine (G).

Question 3

Bonds (3)

Answer 3

1) phosphodiester bond: the phosphate group of one nucleotide bonds with 2 neighbouring sugars

2) hydrogen bond: 3 bonds between C and G, and 2 bonds between T and A

3) Van der Waals interaction: between each base interaction

Question 4

DNA

Answer 4

Desoxyribonucleic acid (double strand helix) with opposite orientation 3’-> 5’ and 5’-> 3’

Question 5

RNA

Answer 5

Ribonucleic acid (single strand) extra OH on the second carbon

Question 6

pyrimidine

Answer 6

(with 1 ring) C , T , U

Question 7

purine

Answer 7

(with 2 rings) A , G

Question 8

semiconservative model

Answer 8

the two created strands each contain one parent strand and one replicated strand

Question 9

Replication of DNA (steps)

Answer 9

1) site begins at origin of replication (bubbles). specific sequence on nucleotide to start the opening.

2) Proteins recognise this sequence and attach to it, separate the two strands and replicate the DNA in both directions until the entire molecule is copied

Question 10

topoisomerase

Answer 10

protein, relieve the strain on the parental DNA

Question 11

helicase

Answer 11

separates the parental DNA in 2

Question 12

primase

Answer 12

synthesises RNA primer using parental DNA as a template

Question 13

single-strand binding protein

Answer 13

stabilizes the unwound parental strand

Question 14

RNA primer

Answer 14

created by primase protein 5-10 nucleotides long. DNA polymerase enzyme recognises the primer and starts adding nucleotides from 3’ -> 5’ direction

Question 15

leading strand

Answer 15

5’ -> 3’ direction. direction matches the direction of the replication fork

Question 16

lagging strand

Answer 16

polymerase works against the direction of the replication fork.

Question 17

Okazaki fragments

Answer 17

on the lagging strand, it is synthesised in a series of fragment

Question 18

Telomeres

Answer 18

special sequence at the end of DNA with no genetic information.

Since enzymes cannot add nucleotides to the 5’ end of a chain, daughter DNA strands get slightly shorter on the 5’ end with every replication

This sequence prevents for any loss of genetic information

Question 19

telomerase catalyzes

Answer 19

enzyme used in eukaryotic germ cells for the lengthening of the telomerase

Question 20

DNA pol III

Answer 20

involved in the synthesis of the leading and lagging strands

Question 21

DNA pol I

Answer 21

involved in the removal of primers from the fragments and replacing the gap by relevant nucleotides

Question 22

DNA ligase

Answer 22

joins the end of the fragments together

Question 23

histones

Answer 23

positively charged protein where the DNA helix is wrapped around

Question 24

nucleosome

Answer 24

group of 8 histones where DNA is wounded twice
a string forms a 10nm fibres. Different type of histones coils the fibre into a 30 nm fibre.

Question 25

Chromatin

Answer 25

Different type of histones coils the fibre into a 30 nm fibre.

Question 26

chromosome

Answer 26

chromatin forms loop around chromosome scaffold containing proteins.
70 nm wide

Question 27

heterochromatin

Answer 27

highly condensed state

Question 28

euchromatin

Answer 28

less compact, more dispersed state

Question 29

exonuclease activity

Answer 29

DNA polymerases “proofread” the created strand and replace any incorrect nucleotides

Question 30

mismatch repair

Answer 30

other enzymes such as Mut S detect the errors such as bumps or valleys, and also remove and replace incorrect nucleotides after DNA replication

they recognize the mother strand because of methylation

Question 31

nuclease

Answer 31

DNA-cutting enzyme

Question 32

nucleotide excision repair

Answer 32

the nuclease cuts the damaged part and the gap is filled by the DNA polymerases and DNA ligase