Punnet Charts?

Question

Sickle cell disease is caused by an autosomal recessive gene. Because the disease causes anemia and pain, parents who have the trait in their families often get tested to see if they carry the gene for the trait.


1.If each parent has one copy of the recessive gene, what are the chances that their children could inherit two copies and have sickle cell disease?


2.If one parent has sickle cell disease and the other parent is not a carrier, then what are the chances that their children would have the disease?



How would I construct a punnet chart for both of these? Be detailed I wanna know HOW you got your answers. Thanks!

Answer 1

There is an example of a Punnet Chart at the link below, the rest you will be able to work out for yourself. Good luck;

Answer 2

i dont know what letter abbreviations for sickle cell anemia your teacher might want you to use. The recessive gene is usually represented by a non-cap letter lets say "a" and the dominant gene is represented by a capitol letter "A".
so for a punnet square you create something like tic tac toe
for answe number 1) what you put into the punnet square is

..... A..... a
A AA....Aa

a Aa....aa
this shows that there is a 1/4 chance that the
child will have sickle cell anemia "aa"

number 2 will look like this: Not a carrier "AA", parent who has it "aa"

......A.....A
a Aa...Aa

a Aa...Aa

the children dont get the disease, however 4/4 of
them become carriers
P.s the dots between the A's are only there to keep an appropriate amount of space between the letters do not put those dots on paper.

Answer 3

You know that: sickle cell is autosomal recessive. This means that both alleles must be recessive to get the disease (aa). A carrier is heterozygous for the gene (Aa), but does not have sickle-cell anemia. (An alternative to autosomal is sex-linked, in which you must consider the sex of the parents).

The punnett square diagrams the possible genetic combinations of offspring

1. Construct a 2x2 grid for the sickle-cell crossing, and label it
__ A a
A |__|__|
a |__|__|
because each parent is heterozygous. Carrying the letters down their respective columns and rows, you get AA, Aa, Aa, and aa possibilities. The probability of getting the disease, aa, is 1/4, then. For the second problem, change the parent alleles and repeat.

Answer 4

1. 25% on this one.

2. 0% chance on this one!

On #1

Make a square with 4 squares in it. Put a big S and a little s on top and a Big S and a little s on the sides of the squares.
Now just fill in so that in the first square you will get SS, 2nd you will get Ss, third you'll get Ss, and fourth you'll get ss. This means that only the ss could give you sickle cell b/c the others are beat out by the big S dominating over the little s.

#2

Same squares, but put 2 little s's on the side, and 2 big S's on top. Now you should get a Ss in all the squares, hence none will be sickle cell b/c all the big S's are dominating all the small s's. Hence, 0%. Hope this helps!

Answer 5

A sickle cell person has [s s]
A carrier has [S s]
A non-carrier has [S S]

So, for number 1,

......[S s]

S..SS..Ss

s..Ss...ss

You have a 25% chance at having a non-carrier, 25% sufferer, and 50% chance carrier.

Just do the same things for the other questions.