Question

A gene is composed of two alleles. An allele can be either dominant or recessive. Suppose that a husband and​ wife, who are both carriers of the​ sickle-cell anemia allele but do not have the​ disease, decide to have a child. Because both parents are carriers of the​ disease, each has one dominant​ normal-cell allele​ (S) and one recessive​ sickle-cell allele​ (s). Therefore, the genotype of each parent is Ss. Each parent contributes one allele to his or her offspring with each allele being equally likely. Complete parts ​a) through ​c) below. (a) List the possible genotypes of their offspring. A. SS, Ss B. SS, ss C. Ss, sS D. SS, ss, Ss, sS

Answer 1

D

Step-by-step explanation:

Sickle-cell anemia is a disease of the red blood cells in the body. Under normal conditions, each blood cell has millions of molecules of hemoglobin.

Hemoglobin is the molecule that allows the reversible binding of oxygen, and each hemoglobin molecule has four haem groups. Each oxygen molecule that needs to be transported through the body, binds to that haem group.

Sickle-cell anemia causes thee red blood cells to change their shape, this reduces the surface area of the cell, which in turn means that less oxygen can be carried by the cell. People of this disease cannot undergo strenuous exercise.

With genetics, we each have two alleles, one from our father and one from our mother. When an offspring inherits a trait, it is a combination of half the mother, and half the father.

Working out the answer:

The father can pass on either "S" or "s", and so can the mother (since they have the same alleles for it).

So the father's "S" allele can combine with either the mother's "S" or "s".

So that combination leads to the offspring having the genotype "SS" or "Ss".

Now combining the father's "s" with the mother's alleles, the combination leads to "sS" or "ss".

This means that the offspring will have the genotypes SS, Ss, sS, ss.

(ss being the genotype for sickle-cell anemia)

Answer 2

The best way to know what happens with the offspring and genotype of some genes is to do a Punnett square.

Here you have two carriers of the disease and you want to know what will happen with the cross of them.

Everything happens randomly with genes but you can know the probabilityes.

Ss x Ss = SS Ss sS ss

Those are all the possibilities.

50% of having a carrier child (Ss)

25% of having a healthy, not carrier, child (SS)

25% of having a child with the disease (ss)