Question

a gene is composed of two alleles. an allele can be either dominant or recessive. suppose that a couple, 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 their offspring, with each allele being equally likely. complete parts (a) through (c).
(a) genes are always written with the dominant gene first. therefore, there are two instances the offspring could have genotype ss (if one contributes the dominant allele and the other contributes the nondominant allele, and vice versa). list the other two possible genotypes of the offspring.
ss, ss
(use a comma to separate answers as needed.)
(b) what is the probability that the offspring will have sickle-cell anemia? in other words, what is the probability that the offspring will have genotype ss? interpret this probability.
the probability is □. in 100 instances where both parents have one dominant normal-cell allele (s) and one recessive sickle-cell allele (s), we would expect approximately □ of the offspring to have genotype ss.
(simplify your answers. do not round.)

Explanation:

Step1: Create Punnett square

Parents' genotypes: \( Ss\times Ss \)

	S	s
s	\( Ss \)	\( ss \)

Step2: Find other genotypes

From Punnett square, other genotypes (excluding \( Ss \)) are \( SS, ss \)

Step3: Calculate probability of \( ss \)

Total outcomes = 4, favorable outcomes (\( ss \)) = 1. Probability \( P(ss)=\frac{1}{4} \). For 100 instances, expected number \( = 100\times\frac{1}{4}=25 \)

Answer:

(a) \( SS, ss \)
(b) The probability is \( \frac{1}{4} \). In 100 instances, we would expect approximately \( 25 \) of the offspring to have genotype \( ss \).