Gene mutation (BIOL5)

Question 1

Define mutation

Answer 1

Changes to base sequence of DNA

Question 2

Mutations are caused by errors during DNA replication…

Answer 2

Substitution - base substituted w/ another (e.g ATG –> ATT)

Deletion - one base deleted (e.g. ATG –> AT) - will change no. bases, cause shift in all triplets

Question 3

Features of mutations

Answer 3

• Base order determines order of amino cids in protein
  
  • mutation may alter amino acid seq, resulting in diff protein

Question 4

Not all mutations affect order of amino acids…

Answer 4

• Genetic code is degenerate - some amino acids coded by more DNA triplets!
  
  • not all substitution results in change of amino acids
• But deletion will! Cause shift in triplets!

Question 5

Mutagenic agents…

Answer 5

• Inc. rate of mutations, though mutations are spontaneous
  
  • e.g UV radiation, ionising radiation, chemicals

Question 6

Mutations can cause genetic disorder and cancer…

Answer 6

• If gamete containing mutation for d/o/cancer is fertilised, mutation will be present in foetus formed - hereditary mutation
• Acquired muation - occur in cells after fertilisation
• If ocurs in genes controlling rate of cell division, can cause uncontrolled cell division
• If cell divides uncontrollably, will result in tumour

Question 7

Genes that control cell division:

Tumour supressor genes

Answer 7

• Slow down division by prod proteins that stop cells dividing/cause them to self-destruct
• Can be inactivated if mutation occurs in DNA seq
• Mutation in genes - protein not produced
  
  • cells divide uncontrollably

Question 8

Genes that control cell division:

Proto-oncogenes

Answer 8

• Stimulate cell division by producing proteins that make cell divide
• Effect of gene can be inc. if mutation occurs in DNA seq
• Oncogene - mutated proto-oncogene
  
  • gene will become overactive
  • stimulate uncontrollable cell division