Inheritance & Testing in Genetic Disease

Question 1

BRCA1 gene

Answer 1

cancer

Question 2

MDP syndrome

Answer 2

metabolic disorder prevents fatty tissue from being stored underneath the skin

Question 3

Autosomal dominant inheritance example

Answer 3

Huntington’s disease

50% offspring
male and female equally affected
every generation

Question 4

Autosomal recessive inheritance what the risk

and example

Answer 4

25% risk in offspring if two carriers
males and females equally affected
cystic fibrosis

Question 5

cystic fibrosis mutation of what

Answer 5

Mutation of the CF transmembrane conductance regulator CFTR

Main defects in the lungs na pancreas due to thicken mucus

Question 6

X linked recessive inheritance
there is no male to male transmission
on x chromosome
transmitted through unaffected female carriers why

Answer 6

as it affects x chromosome , y comes from Man so from woman

females have another x to rescue the phenotype

Question 7

examples of x linked recessive inheritance

Answer 7

haemophilia A and B ( factor 8 gene on x chromosome ( Xq28)

Duchene muscular dystrophy

Question 8

X linked dominant inheritance
males are affected more than females but females less severely
affected males can only transmit to all daughters but none of their sons ( only y goes to son)

affected females transmit to 50% of offspring

what is an example of this

Answer 8

Rett syndrome

Question 9

Y linked inheritance - who does it affect ?

Answer 9

males only

Question 10

mitochondrial inheritance what happens

and why can’t fathers pass on these disorders

Answer 10

change in mitochondrial genome

Fathers do not pass these disorders to their daughters or sons because all of the mitochondrial genome in an offspring comes from maternal contribution.

Question 11

example of mitochondrial inheritance disease

Answer 11

Leber’s hereditary optic neuropathy

Question 12

what are genetic pedigrees

Answer 12

used to recognise different forms of inheritance

Question 13

penetrance

Answer 13

proportion of people with particular genetic change that go on and exhibit signs and symptoms of that particular disorder.
If some people with mutation don’t develop features of disorder the condition is said to have reduced or incomplete penetrance.
eg. Cancer syndrome such as BRAC1 muttuation - 80% high but not 100% so you wont develop it.

Question 14

in what disease are males exclusively affected

Answer 14

x linked recessive disease

Question 15

consanguineous

Answer 15

relating to or denoting people descended from the same ancestor
autosomal recessive

Question 16

In what disease do all affected men only transmit to daughter

Answer 16

X linked dominant disease

Question 17

in what disease can men not pass on the disease

Answer 17

mitocondrial disease

Question 18

Why might i consider a genetic test for patient

Answer 18

Confirm diagnosis 
Allow presymptomatic testing 
Provide accurate assessment of egentic risk - carrier or affected 
Change treatment plan 
Info about prognosis and management 
Reproduction choices

Question 19

Confirm or rule out a specific genetic or chromosomal condition which is suspected due to specific physical signs and symptoms.
Before brith or ant time of life
what test

Answer 19

Diagnostic test

Question 20

what is a pre symptomatic test

Answer 20

For unaffected individuals in families with a confirmed genetic disease with a known mutation

Question 21

what is a carrier test

Answer 21

A carrier for a genetic disorder has inherited one normal and one abnormal allele for a gene associated with the disorder whci is either autosomal recessive or x-linked recessive

Question 22

what gene is CF on

Answer 22

Phe508del homozygous

Question 23

population risk of CF

Answer 23

1/25

Question 24

if both parents are carriers by CF what is risk of carrying it

Answer 24

2/3

Question 25

if both carriers the risk to the foetus is what

Answer 25

1/4

times all together to find calculated risk

Question 26

who is prenatal genetic testing offered to

Answer 26

Women with increase risk of chromosome abnormality in offspring
Couples who are know to carry a genetic disorder

Question 27

on what chromosome is the CFTR gene located and what does it code for

Answer 27

Located on chromosome 7
Codes for the transportation of cAMP (a regulated chloride (Cl-) transporter) called the Cystic Fibrosis transmembrane conductance regulator (CFTR)

Class 1 mutation is a nonsense mutation so a truncation mutation which means that no functional protein is made- no CFTR protein - premature stop codon so no protein made so no thing
Class 2 means that you have a missense mutation and the CFTR protein has become misfolded so it can’t traffic through the endoplasmic reticulum through the golgi to the cell membrane so it becomes degraded
Class 3 and 4 the protein gets to the cell membrane but it doesn’t function very well. It doesn’t transport the chloride
Class 5 we have only small amounts of proteins getting to the cell membrane so not much CFTR at the cell membrane to transport the chloride
Class 6, protein gets to the cell membrane but it isn’t stable so it is quickly ( degraded) endocytosed back into the cell and degraded