Week 106 - Introduction to Medical Genetics Flashcards Preview

MHS > Week 106 - Introduction to Medical Genetics > Flashcards

Flashcards in Week 106 - Introduction to Medical Genetics Deck (18):
1

What is loci?

Location of a gene on a chromosome

2

What is an allele?

Alternative copy of the same gene
- i.e. one gene is maternal and it's allele is paternal

3

What is penetrance?

Proportion of individuals who carry a gene (mutation) that will display the phenotype

4

What are single gene disorders?

Disease caused by a mutation at a single gene loci

5

What is an autosomal dominant disease?

Gene mutation on a non-sex chromosome

Only need to get the gene from one parent

Not possible to be a carrier without the disease

50% chance that offspring will be affected

6

Give examples of autosomal dominant conditions?

Huntington disease - chromosome 4

Marfan syndrome

Familial hypercholesterolaemia

Familial adenomatous polyposis - APC gene

Long QT syndrome - prolonged QT interval

Breast cancer

7

What is an autosommal recessive condition?

Gene mutation on a non-sex chromosome

Both parents have to be carriers

Normally: 25% chance offspring will be affected
- i.e. Rr * Rr

Consanguinity will increase risk in offspring

8

Give examples of autosomal recessive conditions?

Cystic fibrosis

Phenylketonuria

Beta-thalassemia

Sickle cell anaemia

Tay sachs disease

Spinal muscular atrophy

9

What is an X-linked recessive condition?

Gene mutation on the X-chromosome

Males much more likely to be affected
- females would need two of the mutated genes

Father is unaffected (Y, Xo), mother is carrier (Xo,Xr)

25% chance of having an affected son

10

Give examples of X-linked recessive conditions?

Duchenne muscular dystrophy

Haemophilia A

Red-green colour blindness

11

What is an X-linked dominant condition?

Dominant gene mutation on the X chromosome

Father or mother is affected and the other is unaffected

50% chance of having an affected offspring

12

Give an example of an X-linked dominant condition

Charcot-marie-tooth disease

13

What are multifactorial disorders?

Disorders caused by multiple genes in combination with environmental factors
i.e. environment exposure to susceptible individuals

14

Give examples of multifactorial disorders

Type II diabetes mellitus

Essential hypertension

15

What are chromosome disorders?

Caused by aneuploidy (loss or gain) in one or more chromosomes

16

Give examples of chromosome disorders

Trisomy 21 - an extra chromosome 21

Turners syndrome - X => gonadal dysgenesis

Klinefelters syndrome - XXY => hypogonadism + sterility

17

What are somatic cell gene disorders?

Mutations only in cells of the same lineage

- i.e. tumour cell that contains a mutated gene that is passed onto daughter cells

18

What are mitochondrial disorders?

Mutations in mitochondrial DNA
=> maternally inherited as sperm cell mitochondria don't enter the egg