Mutations

Question 1

Define mutation and mutagenesis

Answer 1

Mutation - change of the nucleotide sequence

Mutagenesis - process of mutation generation

Question 2

State 3 effects of genetic mutation

Answer 2

• May cause phenotypic change
• Can be good or bad
• Source of genome variation
• Driving force of evolution
• May cause disease

Question 3

What kind of mutation can be spontaneous? What are the 2 types of this mutation

Answer 3

• Deamination
• Methylation
• Change of cytosine to uracil

Question 4

What are transposons and what is their mechanism in mutation?

Answer 4

• Specific supernumerary DNA sequence

- Sequences transpose as a discrete unit to random sites

Question 5

Describe 2 effects of transposon mutation

Answer 5

• Can change nucleotide sequence
• Can inactivate genes or change gene expression
• Transcribed in certain cell types
• Protein product can be dysfunctional

Question 6

What are the 3 types of single nucleotide polymorphisms?

Answer 6

Anonymous - no known effect
Non-Coding - outside a gene
Coding - inside a gene

Question 7

Name 3 small scale changes of single nucleotide polymorphisms

Answer 7

• Mutagenic event
• Deletion
• Insertion
• Substitution

Question 8

What are the two types of substitution? Define each

Answer 8

Transition - change to the same type of base (purine/pyramidine)
Transversion - change to a different type of base

Question 9

What are the 5 types of large scale mutation?

Answer 9

• Deletion
• Duplication
• Inversion
• Substitution
• Translocation

Question 10

What are the 4 consequences of single nucleotide changes?

Answer 10

• Changes gene product
• Changes amount of gene product
• Changes polypeptide length
• Has no effect

Question 11

What 3 types of mutation can change polypeptide length?

Answer 11

Nonsense mutation - codon converted to stop codon
Stop codon mutation
Frameshift mutation - single base addition or deletion

Question 12

What is synonymous and non-synonymous mutation?

Answer 12

Synonymous - codon is not affected

Non-Synonymous - codon affected

Question 13

What kind of mutation changes the amount of gene product?

Answer 13

Mutations that affect regulatory sequences

Question 14

Name 3 types of structural chromosomal abnormalities

Answer 14

• Deletion
• Duplication
• Inversion
• Substitution
• Translocation
• Isochromosomes
• Ring chromosomes
• Marker chromosomes

Question 15

What are Isochromosomes, Ring Chromosomes and Marker Chromosomes?

Answer 15

Isochromosomes - 2 p arms, no q arms (or vice versa)
Ring Chromosomes - broken chromosome repaired as a ring
Marker Chromosomes - tiny extra bits of chromosomes

Question 16

What 3 conditions result from chromosomal numerical abnormalities? Describe each

Answer 16

Polyploidy - gaining an extra set of chromosomes (3n)
Aneuploidy - abnormal number of chromosomes (+/-1)
Mosaicism - presence of 2 or more cell lines in an individual

Question 17

What technique can be used to analyse mutations?

Answer 17

Cytogenetic testing

Question 18

What is the importance of cytogenic testing?

Answer 18

• Accurate diagnosis and prognosis of clinical problems
• Better clinical management
• Assess future reproductive risks
• Prenatal diagnosis

Question 19

State 2 reasons for a referral for cytogenic testing

Answer 19

• Birth defects
• Infertility
• Recurrent miscarriage
• Solid tumours

Question 20

What is Robertsonian Translocation?

Answer 20

When 2 acrocentric chromosomes fuse together resulting in 45 chromosomes

Question 21

What is reciprocal translocation?

Answer 21

Two fragments break off from two different chromosomes and swap places

Question 22

What are the 3 kinds of reciprocal translocation?

Answer 22

• Alternate segregation (genetically balanced gametes)
• Adjacent 1 (non-homologous centromeres)
• Adjacent 2 (homologous centromeres)