mendelian inheritence

Question 1

How is sickle cell disease inherited?

Answer 1

autosomal recessive

Question 2

What is autosomal recessive?

Answer 2

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.

Question 3

Likelihood of a child of two carriers for sickle cell disease having a child with it?

Answer 3

first thing to know: is she a carrier?- (2/3 chance of being a carrier)
-take affected person out of the picture

Question 4

What is the chance of the daughters baby being affected?

Answer 4

2/3 (her chance of being carrier) x population carrier risk x 1/4

Question 5

What is cystic fibrosis?

Answer 5

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

Question 6

What was the chance of a girl with a brother with CF having the condition- when she was born?

Answer 6

1/4
and now she has grown up-2/3

Question 7

How many people in UK are a carrier of CF?

Answer 7

1/25

Question 8

What is the risk that her baby’s father is a carrier?

Answer 8

1/25

Question 9

What is the chance of a cousin of cystic fibrosis boy having cystic fibrosis?

Answer 9

chance of sister being carrier (1/2) x 1/25 x 1/4 =at birth

Question 10

What is the chance the cousin is a carrier of CF?

Answer 10

1/4

Question 11

What is chance of having a baby that is affected?

Answer 11

1/4 (chance of mother being carrier) x 1/25(dad) x 1/4 (chance they are both carriers)= 1/400

Question 12

What is achondroplasia?

Answer 12

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.

Question 13

Describe how dominant conditions work?

Answer 13

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?

Question 14

Give characteristics of autosomal dominant inheritance?

Answer 14

no skipped generations
equally transmitted by men and women
male to male transmission (not x linked)

Question 15

What is the risk of a man with achondroplasia having his third child have achondroplasia? (spouse doesn’t have)

Answer 15

1 in 2

Question 16

What is chance of grandson having the condition?

Answer 16

zero

Question 17

Describe the outcomes of a mother (carrier of haemophillia) and father (unaffected) having children?

Answer 17

50% chance the son will have haemophillia
50% chance the daughter will have haemophillia

Question 18

Outcomes of a father with haemophilia and unaffected mother?

Answer 18

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

Question 19

What is dystrophin?

Answer 19

gene important in making muscle

Question 20

Describe becker muscular dystrophy?

Answer 20

faulty dystrophin protein - but still there
manifest either with muscle weakness or heart condition (dilated cardiomyophathy)

Question 21

what is the risk of a daughter of affected x linked man being a carrier?

Answer 21

1- inevitable