NNHS AP Biology
Genetic Problem Set
1) In certain trees, smooth bark is dominant over wrinkled. Cross two trees that are heterozygous for smooth bark. If there are 100 offspring produced, what is the likely number that will have smooth bark?
2) In Mountain Boomers, the genes for length of tail exhibit incomplete dominance. Use a Punnett square to predict the result of a cross between a homozygous long tail and a homozygous short tail Mountain Boomer. What is the phenotype of the offspring?
3) In certain bacteria, oval shape is dominant over round shape, and thick cell walls are dominant over thin. Draw a Punnett square to show the cross between a dihybrid oval, thick-walled bacterium with a round thin-walled bacterium. Identify the phenotypic ratio of the offspring.
4) In guinea pigs, black coat color is dominant over white, short hair is dominant over long, and rough coat is dominant over smooth. Show the Punnett square for a cross between a homozygous, black, short-haired rough guinea pig, and a white, long-haired, smooth guinea pig. Identify the phenotypic ratio of the offspring.
5) In humans, the ability to taste phenylthiourea (PTU) is dominant. “Tasters” (TT) or (Tt) perceive an extremely bitter taste, while “non-tasters” (tt) experience no taste.
a) What are the genotypes of Mr. and Mrs. Meadowmuffin, who can taste PTU, and their child who cannot?
b) What offspring phenotypes would be expected from the following crosses, and in what ratios?
i) heterozygous x heterozygous
ii) homozygous taster x heterozygous
iii) heterozygous x non-taster
6) Two fruit flies with normal wings are crossed. Among 123 offspring, 88 have normal wings and 35 have “dumpy” wings. What inheritance pattern is shown by the normal and dumpy alleles? What are the genotypes of the two parents?
7) In cats, B=brown hair color, b=white hair color, $=short hair, and s=long hair. Make a Punnett square for the following crosses:
a) Bb$s x bb$s
b) Bb$s x Bb$s
c) BB$$ x Bb$$
8) In humans, a disease called FH is caused by an incomplete dominance situation. If two heterozygous individuals married and planned to have children, what information would you provide concerning the probability of having children free of the disease?
9) Mary has blood type A and she marries John, whose blood type is B. They have three children, Joan, James, and Pete. Joan has blood type O, James has blood type A, and Pete has blood type B. Draw a Punnett square to show how this is possible.
10) Roan is the name for cattle that show a heterozygous codominant genotype. A roan calf’s parents were a white cow and a red bull. What is a roan’s genotype? Can two roan’s mate and produce all roans? Explain.
11) Flower color in certain plants is governed by epistasis. P=purple, p=white, C=curved petals, c=straight petals. A homozygous recessive petal will cause white petals. Show a Punnett square for the cross Ppcc x PPCc and give the phenotypic and genotypic ratios.
12) In guinea pigs, black is dominant. One half of a particular litter is all white. What are the genotypes of the parents?
13) As a result of crossing two hybrid yellow garden peas, 120 offspring are produced. According to laws of chance, what is the most probable number of yellow offspring?
14) What phenotype should be crossed with black guinea pig to determine whether or not it is purebred?
15) The diagram below shows two generations of deafness in a family. A dark circle represents a deaf female. A clear circle represents a hearing female. Squares represent males. What is the inheritance pattern of the deafness characteristic?
16) In humans, brown eyes are usually dominant over blue eyes. Suppose that a blue eyed man marries a brown eyed woman whose father was blue eyed. What is the probability that their children will have blue eyes?
17) One hundred experimental matings of brown birds with white birds produced speckled offspring. What phenotypic ratio would you predict for the offspring of the speckled birds?
18) In tomatoes, cur leaf is dominant over potato leaf, and purple stem is dominant over green stem. The mating of two plants produced 1790 purple cut, 620 purple potato, 623 green cut, and 222 green potato. What is the most probable genotype the parent plants?
19) Identify three different pairs of parental blood types that could result in a child with Type O blood.
20) There is evidence that a certain color in cats is sex linked. Yellow is recessive to black. A heterozygous condition results in tortoise shell or calico color. A calico cat has a litter of 8 kittens: 1 yellow male, 2 black males, 2 yellow females, and 3 calico females. What was the male parent’s color?
21) Determine the possible blood types from the mating of a person who is homozygous A blood type and a person who is heterozygous B blood type.
22) If a man who has type O blood marries a woman who is heterozygous for B blood, what are the possibilities of them having children with type B blood? Type O blood? Type A blood?
23) Mr. and Mrs. Doe had a child named Bo at the same time Mr. and Mrs. Roe had their son Joe. The Roes took Joe home, and after looking at him they claimed that Joe was not their child. They were going to sue the hospital for the mix-up. The hospital took the blood types of all six individuals. Mr. Roe had type A blood. Mrs. Roe had type A blood. Joe had type O blood. Mr. Doe had type O blood. Mrs. Doe had type AB blood. Bo had type A blood. Was there a mix-up?
24) If a woman is a carrier of the sex-linked trait hemophelia and marries a healthy male, what are the chances of their offspring having hemophilia? What are the chances of their sons having hemophilia? What are the chances of their daughters being carriers?
25) Red-green colorblindness is sex-linked. If a colorblind male marries a carrier female, what are the chances that their sons will be colorblind? What are the chances that their daughters will be carriers?
26) If a woman’s father had hemophilia and her mother was a carrier, what are the chances that she is healthy? What are the chances that she is a carrier?
27) Why are there more males than females with sex-linked traits?