Genetics...Very useful..Very high yield - ia

[ArchivalUser]

Bumping it up for everyone else. Good luck guys!!!

[ArchivalUser]

[ArchivalUser]

thank u very much

[ArchivalUser]

thanks for these Qs!
Im having a hard time understanding one point,can anyone help?

Q1/. A woman who has two brothers with hemophilia A and two normal sons is again pregnant. She requests counseling for the risk of
her fetus to have hemophilia. What is the risk that her next child will have hemophilia?
a. 1
b. 1/2
c. 1/4
d. 1/8
e. 1/16

Probability that she is carrier ½

Q5/. A man whose brother has cystic fibrosis wants to know his risk of having an affected child. The prevalence of cystic fibrosis is 1 in 1600 individuals. The risk in this case is
a. 1/8
b. 1/16
c. 1/60
d. 1/120
e. 1/256

chance to man having a carrier state=2/3

why does the first Q have carrier state 1/2 and the second one has 2/3 ??......both are recessive dis.
can anyone explain please...

[ArchivalUser]

Hi hd12

Hemophilia A is inherited as an X-linked recessive disorder
Cystic fibrosis is inherited as an autosomal recessive disorder.

Mode of inheritance is different.

X-linked recessive disorders:
1. Females are usually carriers because they have a second healthy X chromosome. Men will exhibit the disease because they have one X chromosome.
2. When a healthy male and a carrier female have children, 2 out of 4 children will receive the defective gene. So there is a 50% chance or 1/2 probability that she will be a carrier (because she is female…XX)

Autosmal recessive disorders:
1. If the man's brother exhibited the disease, it means both their parents are carriers.
In this case, out of 4 offspring, 1 will be healthy (not a carrier), 2 will be carriers, and 1 will exhibit cystic fibrosis. Therefore, it means that 2 out of 3 are carriers.
That is why the probability that this man himself is a carrier is 2/3.

[ArchivalUser]

thanks a lot ia.

[ArchivalUser]

In q Nu one if the mother has affected child what is the propaplity then?

[ArchivalUser]

THANX soo much psychmledr for your wonderful explanation!

[ArchivalUser]

hd12, you are welcome

[ArchivalUser]

This is great... Thanks for posting this! I really need to work on genetic calculation problems.