Mutations

Question 1

What is a mutation?

Answer 1

Any change in the DNA sequence of a cell, a change in sequence of nucleotides that makes up a gene

Question 2

Exogenous mutagens

Answer 2

From environment

Question 3

Endogenous mutagens

Answer 3

From inside the body

Question 4

Transposons

Answer 4

Specific DNA sequences that can jump around the genome, they can inactivate or change gene expression

Question 5

Spontaneous deamination

Answer 5

Amine group removed from cytosine/5-methylcytosine and replaced with O -> uracil/thymine
Guanine now pairs with either U or T

Question 6

Spontaneous dimerisation

Answer 6

Bonds formed between adjacent pyrimidine (C or T), associated withUV damage, causes bulges in DNA, can lead to skin cancer

Question 7

Transition base substitution

Answer 7

Change to same type of base: purine to purine, pyrimidine to pyrimidine

Question 8

Transversion base substitution

Answer 8

Change to different type of base: purine to pyrimidine or vice versa

Question 9

SNPs

Answer 9

A single base pair variation in a gene

Question 10

Anonymous SNP

Answer 10

no known effect

Question 11

Coding SNP

Answer 11

Located inside a gene

Question 12

Non-coding SNP

Answer 12

Located outside a gene

Question 13

Missense mutation

Answer 13

Changes one codon, no frameshift

Question 14

Nonsense mutation

Answer 14

Truncated protein

Question 15

Why are deleterious effects maintained in the human population?

Answer 15

1. Depends on genetic drift and selection pressure
2. Some mutations confer other protective benefits to heterozygous

Question 16

Deletion in chromosomes

Answer 16

Loss of a fragment of DNA

Question 17

Duplication in chromosomes

Answer 17

Doubling of a section of chromosome, can affect dosage

Question 18

Inversion in chromosomes

Answer 18

Section of chromosome is excised and reintegrated at 180 degrees to original orientation

Question 19

Translocation chromosomes

Answer 19

Swapping of parts of two chromosomes, may have no effect if no genes are lost

Question 20

Robertsonian translocation

Answer 20

Chromosome breaks at centromere before re-fusing, small fragments can be lost

Question 21

Fragile sites

Answer 21

Areas in chromosomes that are unstained under the microscope

Question 22

Aneuploidy

Answer 22

The presence of an abnormal number of chromosomes in a haploid set

Question 23

Monosomy

Answer 23

The absence of one member of a pair of chromosomes

Question 24

Non-disjunction during mitosis

Answer 24

Can lead to only a subset of cells in the body containing chromosomal mutations.

Question 25

Mosaicism

Answer 25

The presence of two or more cell lines in an individual (throughout the body or tissue specific)

Question 26

Polyploidy

Answer 26

The gain of an entire set of chromosomes, most common cause is polyspermy

Question 27

Amniocentesis

Answer 27

A small sample of amniotic fluid used in genetic testing

Question 28

Techniques used in cytogenetic testing

Answer 28

Karyotyping, fluorescent in situ hybridisation (FISH), microarray hybridisation, DNA sequencing