Probability and Genetics: Videos & Practice Problems

Probability is a measure of the likelihood of an event occurring. Which of the following statements is false about probability?

Albinism is an autosomal recessive disorder which means that only the homozygous recessive genotype will show the disorder. If a male carrier (Aa) crosses with an albino female (aa), then the ratio of unaffected and albino children will be:

Autosomal recessive traits pass from both parents onto their children. Albinism is an autosomal (not sex-linked) recessive trait. Both homozygous dominant (AA) and heterozygous dominant (Aa) individuals will exhibit a normal phenotype, while only homozygous recessive (aa) individuals will be albino. What is the probability that a child of a homozygous dominant father and a heterozygous mother will have albinism?

An X-linked genetic condition known as Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness and degeneration as a result of alterations in a protein known as dystrophin, which aids in the preservation of muscle cells. What is the probability that each child will inherit DMD if an affected man marries a carrier woman?

In cattles, the polled (absence of horn) condition is dominant over horned, and the coat color is controlled by two codominant alleles. The genotype RR produces red coat color, RW produces roan, and WW produces white. A dairy farmer crossed a PpRW bull with a ppWW cow. What is the probability that the offspring of this cross will be polled white?

Bulldog dwarfism is a lethal genetic defect in which fetuses homozygous for the mutation in the ACAN gene have severe disproportionate dwarfism and are usually aborted around seven months of gestation. When two cattle that are heterozygous for the mutation are crossed, what is the probability that the offspring will be of the same genotype as the parents?

Which of the following supports the chromosome theory of heredity?

In a dihybrid cross between AaBb heterozygotes, what is the probability of the offspring genotype being AABB?

What is the probability that a child born to parents who are carriers for an autosomal recessive disorder will also be a carrier?

A couple has two children, both of whom have been diagnosed with cystic fibrosis, an autosomal recessive condition. They are expecting their third child and are concerned about the possibility of cystic fibrosis in their baby. They seek information from a genetic counselor. After discussing their family histories, the counselor said that they are both carriers of this recessive condition. What is the chance that the third child of the couple will be free of the condition?

Galactosemia is a disorder that affects how the body processes a simple sugar called galactose.  The signs and symptoms of galactosemia result from an inability to use galactose to produce energy. Researchers have identified several types of galactosemia. These conditions are each caused by mutations in a particular gene and affect different enzymes involved in breaking down galactose. There are 3 types of galactosemia. Type I, type II, and type III galactosemia are also called?

Galactosemia happens when there's a change (mutation) in the genes that make an enzyme that breaks down galactose. To have galactosemia, a child must inherit two galactosemia genes, one from each parent. If both the parents who were found to be galactosemia carriers are planning for a child, what will be the probability that the child will be a carrier, affected or healthy, respectively?

The autosomal recessive inheritance of galactosemia results in a lack of an enzyme necessary for adequate galactose degradation. Galactose accumulation becomes the substrate for enzymes that catalyze the polyol pathway of carbohydrate metabolism in galactosemic patients.  What is the possible reaction that the accumulated galactose undergoes?

A cross was performed between individuals of genotypes AaBbCcDd and AaBbCcDd. What is the probability that the offspring will have the same genotype as their parents?

A cross was performed between individuals of genotypes AaBbCcDd and AaBbCcDd. What is the probability that their offspring will have the genotype AABbCcDD?

A cross was performed between individuals of genotypes AaBbCcDd and AaBbCcDd. What is the probability that their offspring will have all the four recessive traits?

An unaffected female marries a man who is affected by an X-linked recessive trait. What is the probability that she will conceive an unaffected son? 

a. 0% 

b. 25% 

c. 50% 

d. 100%

If a man with an X-linked recessive trait marries a female who is an unaffected carrier, what is the probability that his daughter is a carrier of the trait?

A dominant X-linked trait is hypophosphatemic rickets. An individual with hypophosphatemic rickets marries a woman who is not genetically predisposed to the disorder. How likely is it that they have an unaffected daughter?

A woman who is heterozygous (Dd) for a dominant gene marries a man who is homozygous recessive. What is the probability of her first child inheriting the dominant allele?

What is the likelihood that a child would have two diseases if both parents are healthy yet carry the genes for both autosomal recessive disorders?

In pea plants, plant height, flower color, and pod color are governed by three independently assorting genes. The three genes have dominant and recessive alleles, with tall (T) dominant to short (t), axial flower (A) dominant to terminal (a), and green pod (G) dominant to yellow (g). If two pea plants that are heterozygous for all three genes are crossed, what is the probability that their offspring will have the genotype TtAaGg?

A dihybrid cross between pea plants with round yellow seed (RrYy) and wrinkled green seed (rryy) is performed. What is the probability of obtaining offspring with wrinkled yellow seeds?

If two parents are both heterozygous for a trait, what is the probability that their offspring will be homozygous recessive for that trait?

What is the probability of rolling a 6 on a fair die?

A jar contains 4 red balls and 6 green balls. What is the probability of drawing a red ball?

What is the probability of drawing a red card from a deck of cards?

What is the probability of flipping a coin and getting heads?

Sickle cell anemia is an autosomal recessive disorder. Suppose we use "a" to denote the recessive allele associated with this condition, which of the following crosses can produce offspring in which 50% are affected by this condition?

The following conditions can be caused by an autosomal dominant inheritance except: