AP Bio Unit 5 Practice Questions
Which of the following is a question that can be answered with a standard Punnett square, regardless of the parents' genotypes?
"How might alleles independently assort during meiosis?"
A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color-blind marries a color-blind male. What is the probability that this couple's son will be color-blind?
1/2
A spermatogonium has the genotype AaBB. What is the likelihood it will produce a haploid cell with genotype AB after meiosis?
1/2
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt x BBtt will have black fur and long tails?
1/2
Huntington's disease is caused by a dominant allele. If one of your parents has the disease, what is the probability that you, too, will have the disease? (only one of your grandparents had the disease)
1/2
Assume that genes A and B are not linked. If the probability of allele A in a gamete in 1/2 and the probability of allele B in a gamete is 1/2, then the probability that BOTH A and B are in the same gamete i
1/2 x 1/2
A woman and her spouse both show the normal phenotype for pigmentation but both had one parent who was an albino. Albinism is an autosomal recessive trait. What is the probability that their first child will be an albino?
1/4
Albinism (lack of skin pigmentation) is caused by a recessive autosomal allele. A man and woman, both normally pigmented, have an albino child together. The couple decides to have a second child. What is the probability that this child will be albino?
1/4
In a cross AaBbCc x AaBbCc, what is the probability of producing the genotype AABBCC?
1/64
n a cross of XxYYZZ and xxYyZz, what is the likelihood of an offspring with genotype xxYyZz?
1/8
In snapdragons, heterozygotes have pink flowers, whereas the two homozygotes have red flowers or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring will have pink flowers?
100%
A couple who are both carriers of the gene for cystic fibrosis have two children who have cystic fibrosis. What is the probability that their next child will have cystic fibrosis?
25%
In sheep, eye color is controlled by a single gene with two alleles. When a homozygous brown-eyed sheep is crossed with a homozygous green-eyed sheep, blue-eyed offspring are produced. If two blue-eyed sheep are mated with each other, what percent of the offspring will most likely have brown eyes?
25%
A couple has had five female babies in a row and the mother is now pregnant again. What is the likelihood she has a girl?
50%
Achondroplasia is caused by a dominant allele and follows a lethal dominant inheritance pattern - individuals that receive two dominant alleles often do not survive to birth, let alone reproduction. If a male with achondroplasia reproduces with a normal female, what is the likelihood their second offspring will also have achondroplasia?
50%
In crossing a homozygous recessive with a heterozygote, what is the chance of getting an offspring with the homozygous recessive phenotype?
50%
A couple who are both carriers of the gene for cystic fibrosis have two children who have cystic fibrosis. What is the probability that their next child will be phenotypically normal?
75%
A 9:3:3:1 phenotypic ratio is characteristic of
A dihybrid cross
What is a genetic cross called between an individual of unknown genotype and a homozygous recessive?
A test cross
Alleles
Are alternative forms of a gene
A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates
Complete dominance
Mendel observed seven traits in pea plants that varied between only two forms. For example, flowers were either purple or white but were never pink or spotted. What type of inheritance is this?
Complete dominance (or simple inheritance)
If genes aren't linked, they frequently separate from one another (Law of Segregation) as a result of which process?
Crossing over
New combinations of linked genes are due to
Crossing over
A chin cleft ("butt chin") appears to have at least some genetic component. However, in order to even have a hope of a chin cleft, a person needs to also have genes for a strong chin (no one with a weak chin seems to have a chin cleft). This effect is best summarized by what concept?
Epistasis
One gene masks the expression of another. What kind of inheritance is this?
Epistasis
Suppose that two very tall parents have a child. The child unexpectedly is born with achondroplasia, which is a condition that causes dwarfism because cartilage is not converted to bone. Given the likely height of the child, which genetic phenomenon is likely occurring here?
Epistasis
There is good evidence for linkage when
Genes do not segregate independently during meiosis
In a small group of people living in a remote area, there is a high incidence of "blue skin," a condition that results from a variation in the structure of hemoglobin. All of the "blue-skinned" residents can trace their ancestry to one couple, who were among the original settlers of this region. The unusually high frequency of "blue skin" in the area is an example of
Genetic drift
Which is an example of a sex-linked condition?
Hemophilia
Which is an example of an autosomal dominant condition?
Huntington's Disease
Using a pedigree, how could you distinguish a Y-linked trait from an X-linked trait?
If the trait is Y-linked, it will be passed down from fathers to all of their sons. An X-linked trait is passed from the mother's side.
The phenotype of the heterozygote differs from the phenotypes of both homozygotes. What kind of inheritance is this?
Incomplete dominance
Roan color in cattle is the result of codominance between red and white color alleles (Rr). How would one produce a herd of pure-breeding roan-colored cattle?
It cannot be done
You notice that a pedigree shows a trait being passed down through a very large family group among only males, and no females. Without any other information (except that these are humans), how is this trait most likely inherited?
It's X-linked and holandric
Mendel's law of segregation was nearly impossible for most biologists to understand until there was a general understanding of
Meiosis
Gene A, Gene B, and Gene C each exist on the same chromosome. The distance from Gene A to Gene B is 9 map units and the distance from Gene C to Gene A is also 9 map units. Which overall process would cause only some of the genes to be passed on together, and which pair of genes is least likely to be inherited together?
Meiosis I separates genes; Genes B and C are least likely to be inherited together.
One example is the ABO blood group system. What kind of inheritance is this?
Multiple alleles
What type of mutation process causes Down syndrome, Klinefelter syndrome, and other trisomic/monosomic disorders?
Nondisjunction
If you could run a blood bank and choose what blood is donated, which type would be the best choice because of its versatility?
O-
Which of the following best describes the parents in a test cross?
One individual has the dominant phenotype and the other has the recessive phenotype
Achondroplasia is a form of dwarfism, whereas acromegaly is a disorder in which many parts of the body grow too much. Since these are effectively just one gene each, yet affect many conditions around the body, this is considered what kind of gene expression?
Pleiotropy
The ability of a single gene to have multiple phenotype effects. What kind of inheritance is this?
Pleiotropy
You discover a remote island that hosts a new species of bird with brightly colored plumage (feathers). Interestingly, there is a range of shades, from a light pink to a rich, dark red, though most birds seem to be somewhere in the middle. What type of inheritance is likely producing these phenotype frequencies?
Polygenic
The frequency of crossing over between any two linked genes is
Proportional to the distance between them
Roan color in cattle is the result of codominance between red and white color alleles (Rr). When two roan cattle are crossed, the phenotypes of the progeny are found to be in the ratio of 1:2:1 (red : roan : white). Which of the following crosses could produce the highest percentage of roan cattle?
Red x white
A child with blood type A is born to a mother with blood type B. If the father has blood type AB, which of the following statements is correct about the mother?
She contributed an i allele, which is recessive to the father's I^A allele.
What is an example of an autosomal recessive condition?
Tay-Sachs
When completing a dihybrid Punnett square and distributing potential allele combinations across the top and side of the 4x4 square, you are actually illustrating which of Mendel's laws?
The Law of Independent Assortment.
A mating pair of monkeys are carriers of a recessive allele. Which of the following is true concerning the inheritance of that allele by their male offspring?
The allele will affect the offspring's phenotype if it is found on the X-chromosome.
In humans, red-green color blindness is a sex-linked recessive trait. If a man and a woman produce a color-blind son, which of the following must be true?
The mother carries the allele for colorblindness.
After performing a cross in fruit flies, you find that a certain trait appears in exclusively male offspring. What would be the most likely explanation?
The trait is X-linked (sex-linked)
Which of the following is the most likely explanation for a high rate of crossing-over (recombination) between two genes?
The two genes are far apart on the same chromosome.
What causes a pair of genes to be considered linked?
They're inherited together/are located near one another on the same chromosome
Achondroplasia follows a lethal dominant inheritance pattern, wherein individuals that inherit a homozygous dominant genotype do not live to reproduction (often not even until birth). What, then, is the most likely explanation for why natural selection has not removed the dominant (achondroplasic) allele?
Those that do not inherit two copies of the gene can survive to reproduction and pass on the allele.
What was the most significant result Gregor Mendel drew from his experiments with pea plants?
Traits are inherited in discrete units and are not the results of "blending."
A plant with purple flowers is allowed to self-pollinate. Generation after generation, it produces purple flowers. This is an example of
True breeding
In peas the trait for tall plants is dominant (T) and the trait for short peas is recessive (t). The trait for yellow seed color is dominant (Y) and the trait for green seed color is recessive (y). A cross between two plants results in 296 tall yellow plants and 104 tall green plants. Which of the following are most likely to be the genotypes of the parents?
TtYy x TTYy
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
X^CX^c and X^CY
