Skip to main content

SC.912.L.16.1 Genetics

Nature of Science

Molecular and Cellular Biology

Organisms, Populations and Ecosystems

Classification, Heredity and Evolution

What You Need To Know

  • You need to know how to use Mendel's laws of segregation and independent assortment to analyze patterns of inheritance.
  • You need to know how dominant, recessive, codominant, sex-linked, polygenic, and multiple allele modes of inheritance cause observed inheritance patterns. 

Example One

Hemophilia is a sex-linked, recessive trait. Which of the following describes the probability of hemophilia in the offspring of a man who does not have hemophilia and a woman whose father is a hemophiliac?

A. Each of their sons will have hemophilia.

B. None of their daughters will have hemophilia.

C. Their sons have a 25% chance of having hemophilia.

D. There is a 50% chance that their daughters will have hemophilia.

CLICK HERE FOR ANSWER

Example Two

Alleles for the A and B blood cell antigens are codominant. The condition where no antigens are present on the blood cells (type O blood) is a recessive trait. Which set of parents can most likely produce a child with type O blood? 

A. one parent with type AB blood, and the other parent with type A blood

B. one parent with type AB blood and the other parent with type O blood

C. one parent with heterozygous type A blood, and the other parent with type O blood

D. one parent with homozygous type A blood, and the other parent with homozygous type B blood

CLICK HERE FOR ANSWER

Example Three

One of the parents of a child has phenylketonuria (PKU), which is caused by recessive alleles. The other parent does not have the PKU alleles. What is the chance that the couple will have a child with phenylketonuria? 

A. 0%

B. 50%

C. 75%

D. 100%

CLICK HERE FOR ANSWER

Example Four

Hitchhiker's thumb (H) is dominant to no hitchhiker's thumb (h). A woman who does not have hitchhiker's thumb marries a man who is heterozygous for hitchhiker's thumb. What is the probable genotypic ratio of their children? 

A. 0% Hh: 100% hh

B. 50% Hh: 50% hh

C. 75% Hh: 25% hh

D. 100% Hh: 0% hh

CLICK HERE FOR ANSWER

Example Five

This diagram shows a pedigree for a recessive genetic disorder.

GENETICS.jpg

What is the genotype of individual 6?

A. XHXH

B. XHXh

C. XHY

D. XhY

CLICK HERE FOR ANSWER

Example Six

This diagram shows a diploid cell with two pairs of homologous chromosomes. 

diploid cell.jpg

Due to independent assortment, what is the possible genetic make-up of gametes produced by this organism?

A. SsTt

B. Ss, Tt

C. S, s, T, t

D. ST, St, sT, st

CLICK HERE FOR ANSWER

Example Seven

The table lists the trials for fruit color where allele R exhibits incomplete dominance over allele R'. 

incomplete dominance.jpg

Heterozygous fruit have orange phenotypes. What percent of offspring are expected to have an orange phenotype if the parent plants are orange (RR') and yellow (R'R')?

A. 25%

B. 50%

C. 75%

D. 100%

CLICK HERE FOR ANSWER

Example Eight

Mendel hypothesized that reproductive cells have only one factor for each inherited trait. This hypothesis is supported by which observation? 

A. Haploid cells are produced by mitosis.

B. Diploid cells are produced by mitosis. 

C. Haploid cells are produced by meiosis.

D. Diploid cells are produced by meiosis.

CLICK HERE FOR ANSWER

Example Nine

A human baby boy inherits a recessive allele from his mother. In which circumstance would he most likely show the trait coded for by the recessive allele?

A. The baby inherits the dominant allele from his father.

B. The allele is on an autosomal chromosome and the baby is a twin.

C. The allele is on the X chromosome.

D. The allele is on the Y chromosome.

CLICK HERE FOR ANSWER 

genetics.jpg
video tutorials.jpg
Introduction to Heredity
Mendelian Genetics
Please select a video file.
Punnett Square Fun
Incomplete Dominance and Codominance
Please select a video file.
Sex-Linked Traits

In Your Book

General Biology - Sections 6.3-6.5, pgs. 177-187; Chapter 7, pg. 198

Honors Biology - Chapter 11, pg. 260

Additional Activity Links