Genetics Flashcards Preview

MIMS > Genetics > Flashcards

Flashcards in Genetics Deck (346)
Loading flashcards...
1

Are any diseases purely genetic

Single mutation diseases

2

Is cancer environmental or genetic

What about complex genetic diseases

Can be Both

Also both genetic and environmental

3

What are de novo mutation diseases

Diseases that occur due to inheritance of a newly arising germ line mutation

Ie affects child but not parents

4

What happens if the de novo mutation occurs within the first 10 cell divisions in the embryo

The person will be a germline mosaic

5

Which de novo mutations are homozygous

NONE
They are always heterozygous as it is essentially impossible for both sperm and egg to harm the same de novo mutation

6

Can de novo mutations be hemizygous

Yes if they involve sex chromosomes

7

What causes Apert syndrome

Ser -> Trp mutation in FGFR2
Increases signalling

8

Give an example of a de novo mutation

22q11.2 deletion syndrome
Chromosome 22 has q11.2 deleted, removing 40 genes

Leads to a susceptibility to psychiatric illness

9

Why are some de novo births more common than others

More frequent mutation or repaired less frequently
Mutation confers a selfish advantage to germ line
Some are caused by different mutations
Mutation may be more compatible with live birth

10

What are many miscarriages causes by

The presence of de novo mutations that are incompatible with embryo development

11

Are de novo mutations usually passed on

No as suffers tend not to have children
The disease mutation is under negative selection

12

What is an inherited single mutation disease

Causes by alleles which segregate in populations

Disease causing variants arise in an individual’s germ line and is passed onto subsequent generations

13

What are the 4 patterns of inheriting an inherited single mutation disease

Autosomal dominant
Autosomal recessive
Sex linked
Mitochondrial

14

What is the chance of inheriting a dominant autosomal disease of 1 parent is affected

50%

15

What is an example of autosomal dominant diseases

Mutation of BRCA1 increasing breast and ovarian cancer susceptibility

Polycystic Kidney disease due to several mutations in PKD1 or 2 (not apparent until 40-50 years)

16

Are autosomal dominant disease alleles under negative selection?

Why

Only weakly

Usually manifest after reproductive age

If they manifest before reproductive age, negative selection is strong

17

What is the founder effect

Give an example

When 1 individual carries a mutation and has offspring, spreading the disease


Lake Maracaibo- 1 woman with Huntington’s settled here and had 10 children. Huntington’s is v common here.

18

Give an example of transheterozygotes

Albinism

2 disease causing loci in same gene present in a population

19

Name a gene associated with albinism

Which alleles have been found

OCA

Missense
Nonsense
Frameshift

20

what causes Ellis van Creveld syndrome

Where is it common

Caused by a splice site mutation in EVC

Amish populations

21

What causes xeroderma pigmentosum

SNV or Indel mutation in NER machinery

22

What are recessive lethals

Name one

What are they observed as in genetic testing

Autosomal recessive diseases that are incompatible with foetal development

Not usually named

An absence of homozygotes

23

If a recessive disease is lethal, what is the chance of a child being a carrier if both parents are carriers

2/3

(Child cannot be born with disease)

24

How many heterozygous recessive alleles do humans ja our that would be highly deleterious if homozygous

~0.6

25

Which populations are most at risk of autosomal recessive disease

Populations with high rates of consanguinity

26

What is reduced penetrance

When the same mutation causes disease in one individual but not in another individual

27

Give an example of reduced penetrance

Phenylketonuria (PKU)

autosomal recessive
Decreased metabolism of phenylalanine
Causes intellectual disability, seizures and mental disorders

Can be treated by low phenylalanine diet

28

What is variable expressivity

Same mutation
Severe symptoms in one patient but mild in another

29

What is a medical geneticist

Diagnose genetic conditions
Counsel couples about the implications of the diagnosis

30

What is SMA

Spinal muscular atrophy

An autosomal recessive neurodegenerative disorder caused by mutations in SMN1 and SMN2

Splice site mutation
Exon skipping leading to protein truncation