3.1.5 Nucleic Acids

Question 1

Translation

Answer 1

mRNA leaves nucleus through nuclear pore
To ribosome
tRNA molecules bring amino acids to ribosome
Specific tRNA molecule for specific amino acid Anticodon of tRNA is complementary to codon on mRNA Two amino acids held close together on ribosome Peptide bonds form between amino acids by condensation reaction
tRNA detaches and collects another amino acid from cytoplasm Ribosome moves along mRNA

Question 2

Transcription

Answer 2

DNA helicase
Breaks hydrogen bonds between bases
Strands separate
One DNA strand acts as a template
Free RNA nucleotides diffuse into position According to complementary base pairing
A with U and C with G
RNA polymerase joins RNA nucleotides together To form phosphodiester bonds
Pre-mRNA spliced to remove introns.
Mature mRNA contains exons

Question 3

What did Watson and Crick discover

Answer 3

DNA was the carrier of genetic code

Question 4

Meselson and Stahl experiment

Answer 4

Used 15N (heavy) and 14N (light)
2 samples of bacteria grown for many generations- 1 in heavy nitrogen broth and 2 in light
Nitrogen used to make DNA
Centrifuge samples
Heavy will settle lower down
Heavy bacteria taken out + put in light N broth
Left for one round replication
Spin in centrifuge
Settle in middle - 1 light strand + 1 heavy
Conservative - heavy DNA would still be together + would settle at bottom. Light would settle at top

Question 5

How is the bond formed between nucleotides

Answer 5

Condensation reaction
Between phosphate and deoxyribose
Catalysed by DNA polymerase

Question 6

Draw a DNA nucleotide