Question

The allele for tay-sachs is a recessive allele that causes death in early childhood. The tay-sachs' prgram has enabled Tim McGraw to determine that he is a carrier and that his wife is not. What are the chances they could have a child with Tay-Sachs?

Answer 1

Answer:

There are no chances for this couple to have a child with Tay-Sachs disease. 0% of the possibilities.

Explanation:

Tay-Sachs disease affects the nervous system and is potentially mortal. It is transmitted from parents to progeny. Tay-Sachs is caused by a defective gene in the 15 chromosome.

The child that recesives two coppies of this defective gene, one from the mother and one from the father, results sick. But if only one of the parents transmits the gene, then the child will be a carrier. This child won't be sick but will transmit the gene to his/her own progeny.  

Available data:

• The allele for tay-sachs is a recessive allele, "t"

• Tim McGraw to determine is a carrier, Tt

• Tim´s wife is not a carrier, TT

Cross:

Parental) TT     x     Tt

Gametes) T   T      T   t

Punnet square)   T         T

                     T   TT     TT

                      t    Tt      Tt

F1) Progeny genotype: 2/4= 1/2 normal, TT

                                      2/4= 1/2 Carrier, Tt

                                       0/4= 0 Sick, tt

What are the chances they could have a child with Tay-Sachs?

There are 0% of the possibilities that this family will get a sick child.

Answer 2

Answer:

The chances they would have a child with Tay-sach's is zero

Explanation:

Since Tim McGraw is a carrier; possessing just one copy of the recessive allele and the normal copy being dominant and his wife is neither a carrier nor a tay-sach's, there is zero percent chance of producing a child with Tay-sach's. This is because the condition is expressed when an individual has two copies of the recessive allele.