Genetic disease

Question 1

What is a genotype?

Answer 1

The physical chromosomes/DNA inherited

Question 2

What is a phenotype?

Answer 2

The expression on a genotype i.e. physical features, behaviours

Question 3

What percentage of 1 heterozygous and 1 normal parent’s offspring will be: heterozygous? homozygous? normal?

Answer 3

50% normal
50% heterozygous

Question 4

What percentage of 1 homozygous and 1 normal parent’s offspring will be: heterozygous? homozygous? normal?

Answer 4

100% heterozygous

Question 5

What percentage of 2 heterozygous parent’s offspring will be: heterozygous? homozygous? normal?

Answer 5

25% normal
25% homozygous
50% heterozygous

Question 6

Give an example of an autosomal dominant disease

Answer 6

Marfan’s syndrome

Question 7

Give an example of an autosomal recessive disease

Answer 7

Lysosomal storage disease

Question 8

What percentage of x-linked disease is passed on?

Answer 8

50% of daughters will be carriers
50% of sons will be affected

Question 9

Give an example of an x-linked disease

Answer 9

Haemophilia

Question 10

What are the types of point mutation?

Answer 10

Missense
Nonsense
Frameshift (insertion/deletion)

Question 11

What is missense?

Answer 11

One base is swapped, causing a different AA chain to be made

Question 12

What is nonsense?

Answer 12

One base is swapped, creating a stop codon - so protein is incomplete bc stopped early

Question 13

What is frameshift?

Answer 13

Shifting of codons due to insertion or deletion - causes disruption of the sequence

Question 14

What can diseased mtDNA cause?

Answer 14

diabetes
heart disease
ptosis
retinitis pigmentosa
Leber’s hereditary optic neuropathy

Question 15

What is Leber’s hereditary optic neuropathy caused by?

Answer 15

4 mutated mtDNA genes cause a lack of enzyme complex 1 in mitochondria, affecting oxidative phosphorylation and the production of ATP

Question 16

Where is a metacentric centromere?

Answer 16

Centre of the chromosome

Question 17

Where is a submetacentric centromere?

Answer 17

Above the centre of the chromosome

Question 18

Where is an acrocentric centromere?

Answer 18

Very high on the chromosome

Question 19

What are the types of structural damage that can occur on a chromosome?

Answer 19

Deletion
Inversion
Ring formation
Translocation
Robertsonian translocation

Question 20

What is inversion?

Answer 20

Swapping of DNA within the same chromosome
Can be on the same or opposite arm

Question 21

What is translocation?

Answer 21

Swapping of DNA between different chromosomes
Can be balanced or non-balanced

Question 22

What is Robertsonian translocation?

Answer 22

Loss of p arms from acrocentric chromosomes and q arms join together

Question 23

How are numeric chromosome abnormalities caused?

Answer 23

Non-disjunction (failure to separate during meiosis)

Question 24

What is aneuploidy?

Answer 24

extra or missing chromosome

Question 25

What is polyploidy?

Answer 25

multiple copies of pairs

Question 26

Give an example of monosomy

Answer 26

Turner's syndrome (missing X)

Question 27

Give an example of trisomy

Answer 27

Down's syndrome (trisomy 21)

Question 28

What can Turner's syndrome cause?

Answer 28

Cardiovascular anomalies Fibrous ovaries (causes infertility)

Question 29

What is a teratogen?

Answer 29

A factor which can cause congenital malformation

Question 30

What causes spina bifida?

Answer 30

Failure of vertebral column to close, leaving spinal cord exposed

Question 31

What does TORCH stand for and what do the diseases have in common?

Answer 31

Toxoplasmosis Other microorganisms Rubella CMV Herpes (HSV2) All neonatal/foetal infections that have similar signs and symptoms