DNA, RNA and Genes

Question 1

What depends on the cell’s protein complement?

Answer 1

Structure, function and activity of the cell

Question 2

What determines proteins expressed in the cell?

Answer 2

complement of genes, therefore gene function essential for growth, development and homeostasis

Question 3

Structure of nucleic acids

Answer 3

base: purine - adenine and guanine,
pyramidine - thymine, cytosine, uracil (single ring)
sugars: RNA - β-D-ribose
DNA - β-D-deoxyribose
phosphates: Pi or pyrophosphate PPi
5’ to 3’
phosphodiester bond between nucleotides has polarity as asymmetric

Question 4

Structure of DNA double helix

Answer 4

2 polynucleotide chains coiled around axis

chains are anti-parallel (5’ to 3’ in opposite directions)

Question 5

How is the DNA double helix stabilised?

Answer 5

H bonds between base pairs

hydrophobic stacking forces (between nitrogenous bases and surrounding water)

Question 6

What is the Watson-Crick pairing?

Answer 6

complementary base pairing

A-T G-C

Question 7

Genetic code

Answer 7

sequence of nucleotides/bases which determine the sequence of amino acids for proteins

Question 8

Models of DNA replication

Answer 8

1. conservative

2. semi-conservative

Question 9

Conservative

Answer 9

all parental DNA conserved in one daughter

2 daughter made, one with all old DNA, one with all new

Question 10

Semi-conservative

Answer 10

half of parental DNA conserved in each daughter molecule

this is the correct model

Question 11

DNA replication process

Answer 11

leading strand: easy and continuous - primer
lagging strand: difficult, discontinuous - fragments then
join
RNA primer removed
DNA polymerase, gap filling
DNA ligase

Question 12

DNA-dependent DNA polymerase

Answer 12

all 4 deoxynucleotide triphosphates needed
DNA synthesis requires RNA primer
dTTP
dATP
dGTP
dCTP

Question 13

What drug functions through the targeting of the DNA replication process

Answer 13

etopside, anti-cancer chemotherapeutic
inhibits topoisomerase II
(eukaryotic DNA replication requires topoisomerase enzymes)

Question 14

RNA species in eukaryotic cells

Answer 14

mRNA, tRNA, rRNA, heteronucleoRNA, 7S RNA, snRNA

mainly rRNA

Question 15

Eukaryotic mRNA

Answer 15

initially produced as hnRNA (introns and exons)
5’ cap
5’ UTR
Ribosome Binding Site (RBS) or Kozak sequence
Start/initiation codon
Coding sequence/open reading frame (ORF)
Termination/stop codon
3’ UTR
poly(A) addition consensus signal
poly(A) tail

Question 16

5’ cap

Answer 16

5’ to 5’ linkage
added post-transcription
used in translation - behins to recruit other factors eg. ribosome

Question 17

5’ UTR

Answer 17

untranslated region
eukaryotic carry 5’ and 3’
carry important information affecting translation and mRNA stability

Question 18

Start/initiation codon

RBS/Kozak sequence

Answer 18

S/I codon - AUG
RBS - ribosome binding site, specific to bacterial mRNAs
Kozak sequence - surrounds codon, RccRccAUGG
-3 and +4

Question 19

Coding region

Answer 19

open reading frame

translation occurs using triplets of bases - codons

Question 20

Termination codon

Answer 20

three possible combinations:
UAG - amber
UAA - ochre
UGA - opal/umber

Question 21

Tail

Answer 21

added post-transcription
non-template-directed polymer of A residues - poly(A)tail
requires consensus sequence: AAUAAA
Poly(A) tail aids in efficient nucleocytoplasmic transport, regulates mRNA stability and translation