mendelian inheritence Flashcards
How is sickle cell disease inherited?
autosomal recessive
What is autosomal recessive?
where you have two alterations in a gene, the parents have both copies of gene (normal and faulty). If faulty gene is given by both, child will have faulty.
Likelihood of a child of two carriers for sickle cell disease having a child with it?
first thing to know: is she a carrier?- (2/3 chance of being a carrier)
-take affected person out of the picture
What is the chance of the daughters baby being affected?
2/3 (her chance of being carrier) x population carrier risk x 1/4
What is cystic fibrosis?
mutation of the gene for the chloride channel in the lungs- does not move chloride ions, causing sticky mucus to build up on the outside of the cell
What was the chance of a girl with a brother with CF having the condition- when she was born?
1/4
and now she has grown up-2/3
How many people in UK are a carrier of CF?
1/25
What is the risk that her baby’s father is a carrier?
1/25
What is the chance of a cousin of cystic fibrosis boy having cystic fibrosis?
chance of sister being carrier (1/2) x 1/25 x 1/4 =at birth
What is the chance the cousin is a carrier of CF?
1/4
What is chance of having a baby that is affected?
1/4 (chance of mother being carrier) x 1/25(dad) x 1/4 (chance they are both carriers)= 1/400
What is achondroplasia?
skeletal dysplasia caused by dominant mutations in a gene called FGFR 3. These are disease alterations that affect protein function and either makes protein non functional or missing or protein that has a gain of function.
Describe how dominant conditions work?
Disturbs the normal pathway through the change in it or altered in such a way that through nonsense mediated decay- the amount of gene in body is halved?
Give characteristics of autosomal dominant inheritance?
no skipped generations
equally transmitted by men and women
male to male transmission (not x linked)
What is the risk of a man with achondroplasia having his third child have achondroplasia? (spouse doesn’t have)
1 in 2
What is chance of grandson having the condition?
zero
Describe the outcomes of a mother (carrier of haemophillia) and father (unaffected) having children?
50% chance the son will have haemophillia
50% chance the daughter will have haemophillia
Outcomes of a father with haemophilia and unaffected mother?
if passes on y-male
male offspring will not get condition as it is an x linked disease and man gives his x to girl offspring
What is dystrophin?
gene important in making muscle
Describe becker muscular dystrophy?
faulty dystrophin protein - but still there
manifest either with muscle weakness or heart condition (dilated cardiomyophathy)
what is the risk of a daughter of affected x linked man being a carrier?
1- inevitable
