Lecture 12

Question 1

What is a mutation?

Answer 1

Change in the nucleotide sequence

Question 2

What is mutagenesis?

Answer 2

The process of mutation generation

Question 3

What is an endogenous source of mutagenesis?

Answer 3

Transposable elements

This is where DNA moves from one chromosome to another or moves within a chromosome.

Can insert itself into a gene and cause mutation

Question 4

Is mutagenesis always bad?

Answer 4

No

It may cause disease but also a source of genome variation and the driving force of evolution

Question 5

What is a single nucleotide polymorphism?

Answer 5

Where a single nucleotide in a codon is changed.

Can be anonymous if no known effect

Non-coding if outside a gene or coding if inside a gene

Question 6

What is a large scale mutation

Answer 6

One involving a chromosome.

Eg deletion
Duplication
Inversion
Substitution 
Translocation (swapping)

Question 7

NB

How is DNA read in transcription?

How is mRNA synthesised?

Answer 7

3’ to 5’ by polymerase

5’ to 3’

Question 8

How is mRNA read in translation?

How is polypeptide synthesised?

Answer 8

5’ to 3’

N to C terminus aka 5’ to 3’

Results in protein right way around- same as its original DNA

Question 9

What types of single nucleotide changes are there?

Answer 9

Anaonymous
Coding
Non coding

Deletion
Insertion
Substitution

Transversion= purine to pyrimidine
Transition= purine to purine etc

Question 10

What causes sickle cell anaemia?

Answer 10

A base substitution or missense mutation

Question 11

What’s an SNP that changes amino acid called?

Answer 11

Missense or non-synonymous

Question 12

What’s an SNP that doesn’t change amino acid

Answer 12

Silent mutation or synonymous

Question 13

What can an SNP lead to?

Answer 13

Incorrect amino acid but if stop codon mutated can lead to a frameshift mutation

Question 14

What is a frameshift mutation?

Answer 14

One in which the polypeptide length is changed

Question 15

What happens if a regulatory sequence gets mutated?

Answer 15

Right recipe but incorrect method

Alter promoter
Alter initiation
Prevent splicing
Reduce mRNA stability

Question 16

What is a robertsonian translocation?

Answer 16

P and q arms break apart. P arms lost and Q arms join together. Usually little problem as p arms have little coding material usually. Causes problems later with meiosis as have one chromosome less

Question 17

What is polyploidy and what is its most common cause?

Answer 17

Extra haploid set of chromosomes. Usually caused by one egg and two sperms

Question 18

What causes aneuploidy?

Answer 18

Non-disjunction in meiosis

Get trisomies and monosomies.

Trisomy and monosomy happens in all chromosomes but only seen in those viable with life. Eg an extra chromosome 2 in down syndrome

Question 19

What is cytogenetic testing?

Answer 19

Examining chromosomes to look for structural abnormalities

Question 20

Chromosomal abnormallities can be balanced or unbalanced, explain?

Answer 20

Balanced= no phenotypic changes (non coding DNA)

Unbalanced= changes (coding DNA)

Question 21

What is a reciprocal translocation?

Answer 21

Exchange of material between non homologous chromosomes

Question 22

What is a Robertsonian translocation?

Answer 22

P arms lost and new chromosome formed acts as one chromosome. Problem with meiosis as only 45 chromosomes but usually no problem for individual as P arms have little genetic information.

Great aneuploidy risk for offspring. Can get balanced, monosomy or trisomy

Question 23

What is the difference between a missense and nonsense mutation?

Answer 23

Missense= SNP resulting in incorrect amino acid

Nonsense= SNP leading to stop codon