Genetics

Question 1

What is incomplete penetrance?

Answer 1

Individual with mutation does not express phenotype

Question 2

What is variable expressivity?

Answer 2

Individuals with mutation have different manifestations of disease

Question 3

What type of nucleic material is in the mitochondria?

Answer 3

Circular double stranded DNA

Question 4

What inheritance is myotonic dystrophy>

Answer 4

Autosomal dominant

Question 5

Which side of DNA does DNA polymerase bind to?

Answer 5

3’

E.g. in mitosis

Question 6

Which side of RNA does RNA polymerase bind to?

Answer 6

5’

E.g. protein synthesis

Question 7

What are enhancers?

Answer 7

Remote non-coding sequences that interact with promoters

Question 8

What is miRNA

Answer 8

Micro RNA

Binds to mRNA and stops translation

Question 9

Define allelic heterogenity

Answer 9

Many different types of mutations in a gene can cause that disorder e.g.: CFTR

Question 10

What term: Many different types of mutations in a gene can cause that disorder

Answer 10

allelic heterogenity

Question 11

Locus heterogenity (non allelic heterogeneity)

Answer 11

Mutations in many different genes can cause the same disorder

Question 12

What term: Mutations in many genes can cause the same disorder

Answer 12

Locus heterogenity

Question 13

Define Mosaicism

Answer 13

Individual has a mixture of mutation and non-mutation bearing cells (mutation post conception)

Question 14

What is uniparental disomy?

Answer 14

When an individual has 2 chromosomes from one parents (the other parent’s paired chromosome is missing) - a particular issue in imprinting

Question 15

Inheritance of Prader Willi Syndrome

Answer 15

Imprinting of parental chromosome 15

Question 16

Features of Prader Willi Syndrome

Answer 16

Obesity and hyperphagia
Mild MR
Osteoporosis
Mental retardation
Delayed/incomplete puberty

Question 17

If Huntington’s disease is inherited, which parent is it worse to be inherited from

Answer 17

Father. Mutation is more unstable if inherited from father (more likely to increase)

Question 18

Duchenne muscular dystrophy

Answer 18

x linked recessive x q21.2 frameshift mutation
dystrophin protein defect
wheelchair by age 10

Question 19

Hardy Weinberg equilibrium equation

Answer 19

p2 + 2pq + q2 = 1
p = probability normal allele
q = probability mutant allele
thus p + q = 1
q2 = probability of having disease
2pq = probability of carrier for disease
ie: normal + carrier + disease = 1

Question 20

carrier - prevalence and back

Answer 20

c –> prev: divide by 4; then square root

prev –> carrier: square then multiply by 4

Question 21

Cowden syndrome

Answer 21

PTEN mutation
hamartomas
breast, thyroid, endometrial
macrocephaly

Question 22

Li Fraumeni

Answer 22

sarcoma

breast, leukaemia, melanoma, colon, pancreas, adrenal cortex, brain

Question 23

Peutz Jegher

Answer 23

intestinal polyposis
mucocutaneous pigmentation
colorectal, gastric, pancreatic, breast, ovarian
STK11 gene mutation