Question

question 28
fertilization results in the formation of a
diploid zygote.
haploid gamete.
diploid somatic cell.
haploid zygote.
question 29
what percentage of mans chromosomes are found in a single sperm cell?
25%
75%
100%
33.3%
50%
question 30
two normal individuals have a child who has cystic fibrosis, an autosomal recessive disease. how did this happen?

Explanation:

• Question 28: Fertilization is the union of a haploid sperm and a haploid egg. The combination of their genetic material results in a diploid zygote. Gametes (sperm and egg) are haploid, somatic cells are diploid but not formed by fertilization, and a zygote is diploid (not haploid).
• Question 29: Sperm cells are formed by meiosis. Meiosis reduces the chromosome number by half. So, a sperm cell contains 50% of the man's chromosomes.
• Question 30: Cystic fibrosis is an autosomal - recessive disease. Let the normal allele be \(A\) and the mutant allele be \(a\). If both parents are normal but carriers (\(Aa\)), when they have children, there is a 25% chance of having a child with the \(aa\) genotype (who will have cystic fibrosis) according to the Punnett square (\(Aa\times Aa\) gives \(AA:Aa : aa=1:2:1\)).

Answer:

• Question 28: A. diploid zygote
• Question 29: E. 50%
• Question 30: Both parents are carriers (heterozygous) for the cystic - fibrosis gene.