Lecture 5 : Translation II (Mutations)

Question 1

When do mutations happen? Where? How?

Question 2

When do mutations happen in genomic sequence?

Answer 2

• Most likely during DNA replication
• Impacts base pairing with AT and GC
• Distances between chains can alter which destabilises hydrogen bonds, takes up different spatial space in nucleus, strand slippage

Question 3

DNA polymerase and mutations

Answer 3

• Mistake 1 in every 100000 nucleotides
• Mistakes corrected during proof reading (fixes 99% of errors)
• Some corrected during mismatch repair
• Incorrectly paired nucleotides that remain following mismatch repair become PERMANENT mutations after cell division.

Question 4

Where in the genome can these mutations happen

Answer 4

• If in UTR regions it doesnt really matter to this protein
• If where the red arrows are, it may have a huge effect
• If mutation in promoter, if between GC box or TATA box or CCAAT box then its ok, but if it happens at beginning of transcriptional start site then we’re cooked

Question 5

How can genomic mutations happen

Answer 5

Induced
- Environmental agents, UV rays, exposure to chemicals

Spontaneous
- Wobble-iduced, replication errors

Question 6

What are point mutations

Answer 6

Point mutations - single base pair (can have no effect)

Substitutions are a type of point mutation, which can be a transition or a transversion substitution

Question 7

What are point deletions ( i guess same principle could apply for point additions)

Answer 7

• A point deletion is a FRAMESHIFT MISSENCE MUTATION
• If a region of termination sequence (x stop codon) is deleted, a frameshift mutation occurs causing EXTENSIVE missence (next codon needs to be searched for)

Question 8

What is frameshift nonsense

Answer 8

• Stop codon introduced

Question 9

What is extensive missence

Answer 9

When a stop codon is mutated and another stop codon needs to be searched for, extending amino acid sequence unwantedly

Question 10

What happens if you add 3 bases after position 3

Answer 10

No frameshift, look if its multiple of 3 or not, but mutation still.

Question 11

Summary

Answer 11

Remember, hydrophobic amino acids may be swapped for hydrophobic amino acids and so little biochemical properties may change

Question 12

Summary 2

Answer 12

Degeneracy, silent mutations