19.1 Mutations & Variation

Question 1

What is a mutation?

Answer 1

change in the genetic material

which may affect phenotype

Question 2

What is a substitution mutation?

What effect do they have?

Answer 2

mutation in which nucleotide(s) replaced with another

changes triplet codon

may or may not change amino acid - degenerate

Question 3

What are deletion/insertion mutations?

What effect do they have?

Answer 3

Removal/addition of nucleotide(s)

changes each subsequent triplet codon - non-overlapping

∴ damaging, produces non-functional protein

Question 4

What is a mutagen?

Answer 4

chemical/physical agent

which causes mutation

Question 5

What are the 3 main types of mutagens?

Answer 5

• PHYSICAL
• CHEMICAL
• BIOLOGICAL

Question 6

Explain how physical mutagens increase the rate of mutation:

Answer 6

ionising radiation

breaks 1 or both DNA strands by breaking bonds

process of repairing can cause mutations.

Question 7

Explain how chemical mutagens can increase the rate of mutation:

Answer 7

deaminating agents

chemically alter bases

Question 8

Explain how biological mutagens can increase the rate of mutation:

Answer 8

• ALKYLATING AGENTS
  
  • methyl/ethyl groups attached to bases >> incorrect pairing of bases during DNA replication
• BASE ANALOGS
  
  • substituted into DNA instead of nitrogenous base, changing base sequence
• VIRUSES
  
  • viral DNA inserted into genome, changing base sequence

Question 9

What is a base analog?

Answer 9

molecules

which can substitute for normal bases

in nucleic acids

Question 10

What are the different effects of mutations?

Answer 10

• NO EFFECT, DAMAGING, BENEFICIAL
• SILENT, NON-SENSE, MISSENSE

Question 11

What 3 effects can a mutation have on an organism?

Answer 11

• NO EFFECT
  
  • phenotype unchanged -
    
    • normally functioning proteins synthesised
• DAMAGING
  
  • negatively affects phenotype -
    
    • non-functional proteins synthesised/not synthesised
• BENEFICIAL
  
  • positively affects phenotype -
    
    • protein synthesised gives advantageous characteristic

Question 12

What is a silent mutation?

Answer 12

mutation in which

there is no change to function or overall structure of proteins synthesised

Question 13

What is a nonsense mutation?

Answer 13

mutation in which

non-functional truncated protein synthesised

∵ codon changed to stop codon

Question 14

What is a missense mutation?

Answer 14

mutation which codes for incorrect amino acid

(missense mutations could also be silent, if the changed triplet codon does not affect the overall structure/function of the protein)

Question 15

What are chromosome mutations?

Answer 15

mutations which affect whole chromosome

rather than single gene

Question 16

What are the different types of chromosome mutation?

Answer 16

• DELETION
• DUPLICATION
• TRANSLOCATION
• INVERSION

Question 17

Chromosome mutations:

What is a deletion mutation?

Answer 17

chromosome mutation in which

chromosome section breaks off & is lost

Question 18

What is a duplication mutation?

Answer 18

chromosome mutation in which

chromosome sections duplicated

Question 19

Chromosome mutations:

What is a translocation mutation?

Answer 19

chromosome mutation in which

section breaks off,

& joins non-homologous chromosome

Question 20

Chromosome mutations:

What is an inversion mutation?

Answer 20

chromosome mutation in which

section breaks off, reverses, & then rejoins

Question 21

State & describe the different chromosome mutations:

Answer 21

• DELETION
  
  • section breaks off & is lost
• DUPLICATION
  
  • chromosome sections duplicated
• TRANSLOCATION
  
  • section breaks off, & joins non-homologous chromosome
• INVERSION
  
  • section breaks off, reverses, & then rejoins