SESSION 13

Question 1

Define mutation

Answer 1

The changing of the structure of a gene, resulting in a variant form which may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement or larger sections of genes and chromosomes

Question 2

Define transposable elements

Answer 2

• specific DNA sequences
• supernumerary (many copies)
• always contained within other DNA molecules; never free
• move (transpose) as a discrete unit
• move (transpose) to random sites
• insertionally inactivate target gene

Question 3

Define mutagenic events

Answer 3

A process by which the genetic information of an organism is changed in a stable manner, resulting in a mutation

• deletion
• insertion
• substitution

Question 4

Define single nucleotide changes (micro)

Answer 4

mutations that change gene products
Misssense mutations:
One amino acid is changed for another

mutations that change the amount of gene product
Mutations affecting translation/ transcription:
- alter promotor activity
- alter translation initiation at AUG
- prevent mRNA splicing
- reduce mRNA stability- as caps cant be added - RNA degrades faster

mutations that change the polypeptide length

• frameshift mutation
• mutations of stop codons
• nonsense mutations -> stop codon created

mutations that do not have an effect
Silent or neutral mutations:
- the base change results on the same amino acid
- the new amino acid has very similar properties
Synonymous mutations -> single base changes that don’t’ result in a change of amino acid

Question 5

Define transition

Answer 5

Base is changed to he same type of base

• > purine to purine (A-G)
• > pyrimidine to pyrimidine (T-C)

Question 6

Define transversion

Answer 6

One type of base is changed to another type of base

-> purine to pyrimidine (A/G C/T)

Question 7

Define missense

Answer 7

One amino acid is substituted for another

E.g. Sickle cell anaemia (Gu-> Val)

Question 8

Define macro mutations

Answer 8

Deletion:
Any number of nucleotides can be deleted, fro a single base to an entire piece of chromosome

Duplication:
A section of the gene is replicated

Inversion:
A segment of a chromosome is reversed end to end

Substitution:
A mutation that exchanges one base for another

Translocation:
Rearrangement of parts between non-homologous chromosomes