Intro

Question 1

Duchenne Muscular Dystrophy is an example of a disorder which is highly what?

Answer 1

Based on genetic factors

Question 2

Spina Bifida and ankylosing spondylitis are influenced more by which factors?

Answer 2

Environmental plays a bigger part

Question 3

What is the recurrence rate in disorders that are primarily environmental?

Answer 3

Low

Question 4

What is the recurrence rate in disorders that are primarily genetic?

Answer 4

High

Question 5

Are environmental disorders common or rare?

Answer 5

Common

Question 6

What is a somatic mutation?

Answer 6

Mutation(s) within a gene(s) in a defined population of cells that results in disease eg breast cancer

Question 7

How many chromosomes does a human have?

Answer 7

46 (23 pairs)

Question 8

A capital letter in an inheritance pattern symbolises what?

Answer 8

A healthy cell/gene

Question 9

In autosomal dominant inheritance what is the ration of female to males affected?

Answer 9

50:50

Question 10

What chance do the offspring of a person who had an autosomal disorder have of expressing the disorder?

Answer 10

50%

Question 11

A trait or disease running from one generation to the next may be described as what?

Answer 11

Autosomal dominant

Question 12

Name three disorders that follow autosomal dominant inheritance?

Answer 12

Myotonic dystrophy,
Huntingdon’s disease
Marfan syndrome

Question 13

Chromosomal deletions and duplications are examples of?

Answer 13

Autosomal dominant conditions

Question 14

Define: Penetrance

Answer 14

The frequency with which a specific genotype is expressed by those individuals that possess it, usually given as a percentage. Huntington disease by 80 years 100% (may be incomplete ie: braca1 80% lifetime chance)

Question 15

Define: Expressivity - give examples

Answer 15

variation in expression - the extent to which a heritable trait is manifested by an individual

Example: BRCA1 +/- ovarian and Breast

Question 16

Define: Anticipation

Answer 16

Symptoms develop at earlier ages each time it is passed on!

Myotonic and Huntingdon’s

Question 17

What is a de novo mutation?

Answer 17

New mutation that has occurred during gametogenesis or in early embryonic development.

Question 18

When might a recessive disorder be more likely to occur in offspring of affected individuals?

Answer 18

Consanguineous relationships

Question 19

Relatives of an individual with a recessive condition may be what?

Answer 19

Asymptomatic carriers

Question 20

What percentage risk is there to offspring if two parent shave a recessive gene?

Answer 20

25%

Question 21

What is the risk of offspring being an unaffected carrier?

Answer 21

2/3

Question 22

Name 3 common recessive conditions?

Answer 22

CF
Haemochromatosis
Sickle Cell

Question 23

Who is affected by X linked mutations?

Answer 23

Males always, but females may be affected mildly through to fully affected or not at all

Question 24

Can male to male transmission of X linked occur?

Answer 24

No

Question 25

Name three X linked disorders

Answer 25

Fragile X Haemophilia Red/Green colour blind

Question 26

What are the % chances of carrier normal and affected offspring in an X-linked disorder (mother carrier)

Answer 26

25% normal girl + 25% Carrier girl 25% normal boy + 25% AFFECTED boy

Question 27

If an affected father with an x-linked condition had off spring what would the result be?

Answer 27

All carriers (daughters) males are unaffected

Question 28

what are two factors influencing the expression of female phenotypes in X-linked?

Answer 28

X inactivation | X dominant Vs X recessive inheritance

Question 29

Why does x inactivation occur? What else is it called?

Answer 29

Prevents double chromosome expression in women (lyonisation)

Question 30

rett syndrome is an example of what and how does it affect males?

Answer 30

X linked dominance rare and lethal to males

Question 31

X linked recessive disordes include/

Answer 31

Colour blindness Haemophilia Duchene's

Question 32

Girls can be fully affected by x linked if what happens?

Answer 32

X linked and fully affected if mutation from mum and dad

Question 33

Maternal diabetes and deafness are examples of what type of inheritance

Answer 33

mitochondrial

Question 34

How many genes in mitochondrial DNA?

Answer 34

27

Question 35

What is the % risk of congenital birth defects in blood relatives?

Answer 35

5-6% gen pop 2-3%