Genetics
Problems
- A heterozygous plant with green pods (Gg) was crossed with plant with homozygous yellow pods. Draw the table and explain possible phenotype and genotype of the offspring
- John had met with an accident and need immediate blood transfusion. His blood type is AB. He may receive a transfusion from what blood types? Explain
- A man with the blood type A marries a woman with blood type B. Their first child has blood type O. What other blood types may be expressed in their children.
- Mendel crossed a round seeded F2 plant with a wrinkled seeded plant and observed the following results.
50% of the offspring had round seeds and
50% of the plants produced had wrinkled
What were the genotypes of the F2 round seeded plant and the F2 wrinkled seeded plant used in this course?
- In mink,
brown fur is controlled by dominant gene “B”. Its recessive allele “b” produces
silver blue mink. A brown mink is given to you as a present. You do not know
whether it is homozygous(BB) or
heterozygous(Bb)
- Explain how you would ‘test cross’ this individual
- Diagram a cross to show what type of offspring you would expect if the brown mink were homozygous.
- Diagram a cross to show what type of offspring you would expect if the brown mink were heterozygous.
- In
turkeys, the normal bronze color is
produced by a dominant gene “B”. Its recessive allele “b” produces red color. An independently assorting dominant gene, “N”
produces normal feathers. Its recessive allele “n” produces hairy feathers.
- Diagram a cross through the F2 generation between a homozygous bronze turkey with normal feathers (BBNN) and a red turkey with hairy feathers. (bbnn)
- Diagram a cross through the F1 generation between a heterozygous bronze turkey with normal feathers and a red turkey with hairy feathers.
- Kirk Douglas has a prominent dimple in his chin and so does his son Mike. Dimples are inherited as a dominant trait. If Mike’s mother does not have dimples, and Mike’s wife does not have dimples, what is the probability that Mike’s son will have dimples?
- About 70% of Americans perceive a bitter taste from the chemical phenylthiocarbamide (PTC). The ability to taste this chemical results from a dominant allele (T) and not being able to taste PTC is the result of having two recessive alleles (t). Albinism is also a single locus trait with normal pigment being dominant (A) and the lack of pigment being recessive (a). A normally pigmented woman who cannot taste PTC has a father who is an albino taster. She marries a homozygous, normally pigmented man who is a taster but who has a mother that does not taste PTC. What are the genotypes of the possible children (choose all that apply)?
- Woodrats are medium sized rodents with lots of interesting behaviors. You may know of them as packrats. Let’s assume that the trait of bringing home shiny objects (H) is controlled by a single locus gene and is dominant to the trait of carrying home only dull objects (h). Suppose two heterozygous individuals are crossed. How many of each genotype would be expected if only 4 offspring were produced?
- Suppose you have two rose plants, both with pink flowers. You cross the two plants and are surprised to find that, while most of the offspring are pink, some are red and some are white. You decide that you like the red flowers and would like to make more. What cross would you perform to produce the most red flowered plants?
- A boy, whose parents and grandparents had normal vision, is color-blind. What are the genotypes for his mother and his maternal grandparents? Use XB for the dominant normal condition and Xb for the recessive, color-blind phenotype
- In humans, sickle cell anemia is a disease caused by a mutation of a single locus gene which codes for an important blood protein. The allele for the normal protein (S) is dominant to that for the one causing sickle cell anemia. What gametes would be produced by individuals resulting from a SS x ss cross?
- A man with group A blood marries a woman with
group B blood.
- What are the genotypes of these individuals?
- What blood groups and frequencies would you expect in offspring from this marriage?
- Phenylketonuria (PKU) is an inherited disease caused by a recessive allele. If a woman and her husband are both carriers, what is the probability of each of the following?
- all three
of their children will be of normal phenotype
- one or more of the three children will have the disease
- all three children will have the disease
- at least one child out of three will be phenotypically normal
(Note: Remember that the probabilities of all possible outcomes always add up to 1)
- Karen and Steve each have a sibling with sickle-cell disease. Neither Karen, Steve, nor any of their parents has the disease, and none of them has been tested to reveal sicklecell trait. Based on this incomplete information, calculate the probability that if this couple should have a child, if the child will have sickle-cell anemia.
- A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits (5). Extra digits is a dominant trait. What fraction of this couple’s children would be expected to have extra digits?
- The pedigree below traces the inheritance of a vary rare biochemical disorder in humans. Affected individuals are indicated by filled-in circles and squares. Is the allele for this disorder dominant or recessive? What genotypes are possible for the individuals marked 1, 2, and 3.
- Imagine you are a genetic counselor, and a couple planning to start a family came to you for information. Charles was married once before, and he and his first wife had a child who has cystic fibrosis. The brother of his current wife Elaine died of cystic fibrosis. What is the probability that Charles and Elaine will have a baby with cystic fibrosis? (Neither Charles nor Elaine has the disease)
- In guinea pigs, the allele for short hair is dominant.
- What genotype would a heterozygous short haired guinea pig have? _______ What genotype would a purebreeding short haired guinea pig have? _______
What genotype would a long haired guinea pig have? ________
- Show the cross for two heterozygous guinea pigs.
What percentage of the offspring will have short hair? ________
What percentage of the offspring will have long hair? _______
- In humans, being right-handed (R) is dominant over being left handed (r), and normal vision is dominant over color blindness (which is sex-linked). Two right-handed parents with normal vision have a son who is left-handed and color-blind. Determine the genotypes of the son and both parents. What can you tell me about the phenotypes of the parents?
