DNA and RNA

Question 1

What’s the difference between RNA and DNA?

Answer 1

Deoxyribose and Ribose
Uracil instead of thymine
DNA - 2strands, RNA - 1strand

Question 2

Whats a mononucleotide made of?

Answer 2

Sugar, Base, Phosphate

Question 3

How do mononucleotides join together to form a polynucleotides?

Answer 3

Condensation reaction that forms phosphodiester bonds between the phosphate groups

Question 4

How is a double helix formed?

Answer 4

2 DNA polynucleotide strands join together by hydrogen bonding between bases by complementary base pairing
Two antiparallel strands twist to form the DNA helix

Question 5

How many bonds between A and T, C and G

Answer 5

A and T - 2

C and G - 3

Question 6

Describe transcription

Answer 6

RNA polymerase breaks the hydrogen bonds in the DNA and the DNA unzips
DNA strand becomes a template and nucleotides line up and form hydrogen bonds with complementary base pairing forming mRNA
Leaves through the nuclear envelope and DNA zips up

Question 7

Describe translation

Answer 7

mRNA moves to the ribosome
tRNA moves to the ribosome and the anticodon bonds to the mRNA via complementary base pairing
Another tRNA bonds and a peptide bond forms between the amino acids
the left over tRNA moves away leaving a peptide chain
Stop codon stops the translation and peptide chain moves away from the ribosome

Question 8

Describe semi conservative replication

Answer 8

DNA helicase breaks the hydrogen bonds between bases causing the DNA to unwind
Both strands are templates
Free nucleotides line up and a condensation reaction occurs to form hydrogen bonds between the bases
2 double helixes form - each having an old and a new strand

Question 9

Describe the difference between mRNA and tRNA

Answer 9

mRNA - nucleus, and carries genetic code to the cytoplasm

tRNA - cytoplasm, binding site for amino acids and an anticodon

Question 10

What are mutations?

Answer 10

Change in the base sequence of DNA

Question 11

What causes mutations?

Answer 11

Inversion, deletion, insertion, substitution

Question 12

What do mutations do?

Answer 12

Causes a change in primary structure changing amino acids and therefore tertiary structure

Question 13

Describe mutations in CF

Answer 13

CFTR channel open so less chloride ions, not working

DF508 - deletes 3 nucleotides loss of phenylanine misfolding the protein

Question 14

Define genome

Answer 14

All genes in an individual

Question 15

Describe ring structure of A,G,T and C

Answer 15

A&G have 2 ring structure, T&C have 1 making 3 ring structures overall

Question 16

Describe genetic code

Answer 16

Non-overlapping: each base triplet is read in sequence, separate from the triplet before and after
Degenerative - several triplets can code for the same amino acid
Stop and start codon - Stop UAG

Question 17

What is Meselson and Stahl’s model?

Answer 17

DNA from Ecoli had been grown in medium with heavy isotope Nitrogen
All nucleotides contain heavy N and DNA denser than normal
Bacteria moved into a medium with normal isotope - all new nucleotides incorporated into replicated DNA were light
Bacteria is allowed to divide and their DNA replicate once, extracted and centrifuged
Test tube is dissolved in solution and centrifuged heavy DNA sinks to bottom and light at top
Single band of medium - reject conservative
DNA extracted and centrifuged after 2 rounds - one medium and one light

Question 18

Describe sickle cell anemia?

Answer 18

Sub in gene for haemoglobin A replaces T
mRNA has GUA not GAA
Non polar valine rather than polar glutamic acid so haemoglobin is less soluble