Topic 4c - DNA replication, transcription & translation

Question 1

How many H bonds between T & A?

Answer 1

2

Question 2

How many H bonds between G & C?

Answer 2

3

Question 3

Where does bonding of nucleotides occur?

Answer 3

between the 3rd carbon of the sugar molecule of the upper nucleotide and the phosphate of the lower nucleotide

Question 4

Human chromosomes range in length from ? to ?…?

Answer 4

from 23 million to 246 million bases

Question 5

How fast is eukaryotic DNA replicated?

Answer 5

50 bases per second

Question 6

T or F - DNA molecules are replicated in small chunks simultaneously

Answer 6

true - use replication bubbles

Question 7

Transcription occurs where & produces what?

Answer 7

Nucleus & produces mRNA

Question 8

Translation occurs where and produces what?

Answer 8

cytoplasm & produces proteins from amino acids from nucleotide sequences in mRNA

Question 9

Stages of transcription…

Answer 9

1. Initiation - RNA polymerase binds to promoter region of DNA separating double helix near promoter
2. Elongation - RNA polymerase travels along DNA template strand synthesising RNA by catalysing addition of ribose nucleotides into RNA molecule.
3. Termination - end of gene, RNA polymerase encounters termination signal (DNA sequence) -> RNA polymerase detaches from DNA & releases RNA molecule
4. Conclusion of transcription - DNA rewinds into double helix. RNA -> cytoplasm for translation. RNA moves to another gene for transcription once again

Question 10

T or F - in prokaryotes there is simultaneous transcription & translation

Answer 10

true

Question 11

Stages of translation…

Answer 11

1. Initiation - tRNA + met bound to small ribosome subunit (preinitiation complex); then the complex binds to mRNA (tRNA anticodon pairs with AUG); then large subunit binds to small subunit & met tRNA binds to P site on large subunit
2. Elongation - second tRNA pairs with next codon at A site on large subunit; catalytic site catalyses peptide bond formation between 2 amino acids now at the A site; then the empty tRNA fucks off while the tRNA with the 2 AA’s moves to the P site and leaves the A site vacant.
3. Termination - This is repeated until a stop codon is encountered, then mRNA & peptide are released from ribosome & subunits separate.

Question 12

Different types of mutation…

Answer 12

• nucleotide substitution
• insert mutation (frame shift)
• deletion mutation (frame shift)
• inversion (DNA segment inverted)