genetics- question bank

Eukaryotic cells differ from prokaryotic cells in that…

None of the other choices is correct

Wrong: prokaryotes do not have DNA.; only prokaryotes have a true nucleus; only eukaryotic cells contain genetic material.

In a typical three factor cross between a heterozygous female and a homozygous recessive male, offspring arising from non-crossover gametes will be

A. the most common offspring

B. the least common offspring

C. females only

D. males only

A. the most common offspring

In Drosophila, B is the allele for wild type body color and b is the allele for black body color. A second gene controls wing shape. The shape can be either wild type (V) or vestigial (v). A fly whose genotype is BbVv has wild type body color and wild type wings. A cross is made between BbVv flies and flies with black body and vestigial wings. The following phenotypes were observed among the offspring:

Phenotype: # Observed:

Wild Type: 405; Normal, vestigial: 85; Black, normal: 100; Black, vestigial: 410

Which statement is correct?

A. the genes are linked.

B. there’s evidence of epistasis.

C. the genes are on the same chromosome but assort independently.

D. the genes are on two different chromosomes.

A. the genes are linked.

In Drosophila, B is the allele for wild type body color and b is the allele for black body color. A second gene controls wing shape. The shape can be either wild type (V) or vestigial (v). A fly whose genotype is BbVv has wild type body color and wild type wings. A cross is made between BbVv flies and flies with black body and vestigial wings. The following phenotypes were observed among the offspring:

Phenotype: # Observed:

Wild Type: 405; Normal, vestigial: 85; Black, normal: 100; Black, vestigial: 410

What is the genetic distance between the two genes?

A. 185 map units

B. 18.5 centiMorgans

C. genetic distance is not applicable because the genes assort independently.

D. there’s actually not enough information presented to tell.

B. 18.5 centiMorgans

In “sex-influenced inheritance,”…

A. a trait can be expressed in one sex only.

B. a given genotype produces a different phenotype in males versus females.

C. a given trait is on the X chromosome.

D. fathers never pass the trait to sons.

B. a given genotype produces a different phenotype in males versus females.

When two genes fail to assort independently, the term normally applied is..

A. Mendelian inheritance.

B. incomplete dominance.

C. linkage.

D. complementation.

C. linkage.

Referring again to Tay-Sachs, if two healthy people who are both heterozygous for the disease allele have a child, what is the probability that the child will have Tay-Sachs?

A. 1/4

B. 2/3

C. 1/2

D. 3/4

A. 1/4

Consider two genes A an B that assort independently and have an epistatic relationship. Consider the cross AaBb x AaBb. Which of the following is true?

A. 9/16 with have the genotype AABB.

B. A must be codominant to B.

C. 3/16 of the offspring are expected to have the genotype AAbb

D. none of the other choices is correct

D. none of the other choices is correct

Consider a cross between two people with the following genotypes:AaI^AI^B x AaI^AI^B where alleles A and a display simple dominance/recessiveness for pigmentation (pigmentation is dominant) and I^A and I^B are blood type alleles. What fraction of the children should be albino (no pigmentation) with blood type AB?

A. 6/16

B. 3/16

C. 2/16

D. 1/16

C. 2/16

Consider a gene with alleles "B" and "b". Suppose that the homozygous recessive genotype bb is lethal during embryonic development. In a cross between two heterozygotes, Bb x Bb, what percentage of the offspring born should be Bb?

A. 1/2

B. 1/3

C. 1/4

D. 2/3

D. 2/3

Consider three independently assorting genes A, B, and C. What is the probability of obtaining an offspring that is AaBBcc from parents that are AABbCc and AaBbCc?

A. 1/8

B 1/4

C. 1/16

D. 1/32

D. 1/32

If a child is blood type A and the mother is blood type B, what blood type could the father not be?

A. A

B. B

C AB

D. Bombay

B. B

Red-green color blindness is X-linked recessive. A color-blind woman has children with a man having normal vision. Which statement is correct?

A. No daughters should be colorblind.

B. All sons should be colorblind.

C. The woman’s father was colorblind.

D. All of the other choices are correct.

D. All of the other choices are correct.

A tall, violet plant is crossed with a dwarf, white plant and all of the F1 offspring are tall, violet. The F1 plants are selfed to produce the F2 generation. What fraction of the F2 generation would you expect to dwarf, white? (Assume independent assortment.)

A. 1/4

B. 9/16

C. 3/16

D. 1/16

D. 1/16

With respect to genes A though F, how many genetically distinct gametes can be formed by an individual of the following genotype:AABBCCDDEEFF?

1

Liza has a male cat has short hair, a stubby tail, and extra toes. Alannah has a female cat with long hair, a long tail, and extra toes. The genes and alleles are as follows: L = short hair; l = long hair; M = stubby tail; m = long tail; P = extra toes; p = normal number of toes

Liza’s cat and Alannah’s cats get together and the two cats have kittens. One kitten has long hair, a long tail, and a normal number of toes. What is the genotype of Liza’s cat, the father?

A. LL MM PP

B. Ll Mm PP

C. ll mm pp

D. Ll Mm Pp

D. Ll Mm Pp

In somatic cells, sister chromatids…

A. exist in the G1 stage of the cell cycle.

B. are not usually identical to one another.

C. are produced during S phase.

D. none of the above, because they only exist in germline cells.

C. are produced during S phase.

What is the probability that in an organism with a haploid number of 7, a sperm cell will be formed that contains all 7 chromosomes whose centromeres were derived from paternal homologs?

A. (1/2)^10

B. (1/2)^7

C. (1/7)^2

D. zero

B. (1/2)^7

In each of Mendel's monohybrid crosses of pea plants, the trait that disappeared in the F1 generation

A. illustrated the principle of independent assortment.

B. disappeared in the F2 generation.

C. is the mutant trait.

D. none of the other choices is correct.

D. none of the other choices is correct.

In each one of Mendel's dihybrid crosses,…

A. simple dominance and recessiveness was observed.

B. the phenotypes in the F2 generation segregated in a 9:3:3:1 ratio.

C. epistasis was not evident.

D. all of the above.

D. all of the above.

In the cross (AaBb x AaBb), the genotype AABb should occur at what frequency? (Assume independent assortment in all questions unless stated otherwise.)

A. 1/4

B. 1/8

C. 1/2

D. 1/16

B. 1/8

In a cross between two plants of the following genotypes: (AaBb x AaBb), which one of the following genotypes should occur at the highest frequency among the offspring?

A. AaBb

B. AABb

C. AaBB

D. AABB

A. AaBb

A bivalent contains…

A. a total of four chromatids

B. a total of two chromatids

C. a pair of nonhomologous autosomes

D. none of the above

A. a total of four chromatids

6. During which step of meiosis does recombination occur?

A. None, since meiosis normally produces genetically identical cells.

B. Telophase I

C. Prophase I

D. Prophase II

C. Prophase I

The phase of the eukaryotic cell cycle that occurs before the phase when chromosomes are replicated is known as

A. S phase

B. G1 phase

C. G2 phase

D. mitosis

B. G1 phase

Homology occurs when 2 ___ of a species are the same length and have identical ___ placement

A. chromosomes; centromere

B. centromeres; mitosis

C. telomeres; tissue

D. cells; nuclei

A. chromosomes; centromere

A normal diploid somatic cell from a certain rodent has a total of 22 pairs of homologous chromosomes. How many telomeres are in a somatic cell from this rodent in the G2 phase of the cell cycle?

A. 88

B. 44

C. 22

D. 176

D. 176

Eukaryotic cells differ from prokaryotic cells in that

A. only eukaryotes have true genetic material.

B. prokaryotes have a nucleus whereas eukaryotes have a nucleoid region

C. prokaryotes have a nucleoid region whereas eukaryotes have a nucleus.

D. None of the other choices is correct.

C. prokaryotes have a nucleoid region whereas eukaryotes have a nucleus.

An allele is…

a form of a gene

If two chromosomes of a species are the same length and have similar centromere placement but are not homologous, then…

the chromosomes do not contain the same set of genes

The stage in the eukaryotic cell cycle right after the stage when chromosomes are replicated is known as…

G2 phase

Karyotypes are made using chromosomes at which stage of mitosis?

metaphase

If a typical diploid somatic cell of an organism has 16 pairs of chromosomes, what is the total number of “p” chromosome arms in the G1 phase of the cell cycle?

32

During spermatogenesis in an animal species, one tetrad undergoes nondisjunction during the first meiotic division. Following the second meiotic division, how many of the four gametes produced should contain an abnormal number of chromosomes?

4

The synaptonemal complex…

forms during prophase 1 of meiosis

For an organism of genotype Aa, each somatic cell contains both the “A” allele and the “a” allele, but half of the organism’s gametes contain only the “A” allele and the other half contain only the “a” allele. This is essentially Mendel’s principle of…

segregation

Pigeons may exhibit a checkered or plain color pattern. When checkered pigeons were crossed with plain pigeons, 38 F1 offspring were produced and they were all checkered. When the checkered F1 offspring were crossed, 28 checkered and 9 plain offspring were produced. From this data, the simplest conclusion is…

checkered is dominant to plain

A recessive allele in tigers causes a white coat color. Two normally pigmented tigers are mated and produce a white offspring. The two adult tigers later produce a second offspring. What is the probability that the second offspring has a white coat color?

1/4

In each one of Mendel's dihybrid crosses,…

simple dominance and recessiveness were seen

In a cross AaBbCc x AaBbcc, where capital letters refer to dominant alleles, what is the probability of producing an offspring that has a recessive phenotype for all three characteristics? (Assume independent assortment.)

1/32

A 9:3:3:1 ratio of phenotypes in the F2 generation of a dihybrid cross…

indicates that the dihybrid cross is basically equivalent to two independent monohybrid crosses

In corn, purple kernels are dominant over yellow kernels and full kernels are dominant over shrunken kernels. A true-breeding plant with purple, full kernels is crossed with a plant with yellow, shrunken kernels. The F1 plants have purple, full kernels. In the F2 generation, what proportion of the plants would be expected to have yellow, full kernels?

3/16

In a cross between two plants of the following genotypes: (AaBb x AaBb), which one of the following genotypes should occur at the greatest frequency among the offspring?

AaBb

If an individual has the genotype AaBbCcDD and all four genes assort independently, how many different types of gametes should that individual produce with respect to the four genes?

8

Each of the following statements about meiosis is true EXCEPT…

the complete process of meiosis always produces four gametes

In terms of genetic content,…

all of the other choices are correct: sister chromatids are identical right after DNA replication.; homologous chromosomes are not identical.; sister chromatids do not remain genetically identical throughout meiosis.

In animals, how many functional sperm are normally produced from one complete round (both divisions) of meiosis in a male?

four

Red-green color blindness is X-linked recessive. A woman having normal vision has a colorblind father. She has a daughter with a color-blind man. What is that probability that the daughter is colorblind?

1/2

Consider a gene with alleles A and a. Suppose that the homozygous recessive genotype aa is lethal during embryonic development. Consider two other genes, B and C that assort independently from gene A and have no interactions with gene A. In a cross between two individuals, AaBbCc x AaBbCC, what percentage of the offspring should die during embryonic development?

1/4

Questions 25 – 27 deal with cystic fibrosis which is a rare autosomal recessive disorder. The relevant alleles are C and c, and the genotype leading to the disease cystic fibrosis is cc.

A healthy man, John, has a brother who has cystic fibrosis. John’s parents are healthy. What is the probability that Johns’ brother is homozygous cc for the cystic fibrosis allele?

100%

Questions 25 – 27 deal with cystic fibrosis which is a rare autosomal recessive disorder. The relevant alleles are C and c, and the genotype leading to the disease cystic fibrosis is cc.

a healthy man named John has a brother who has cystic fibrosis. John’s parents are healthy. What is the probability that John’s mother is heterozygous (Cc) for the cystic fibrosis allele?

100%

Questions 25 – 27 deal with cystic fibrosis which is a rare autosomal recessive disorder. The relevant alleles are C and c, and the genotype leading to the disease cystic fibrosis is cc.

John from question 25 actually has two uncles on his father's side. One uncle has the autosomal recessive disease cystic fibrosis, the other uncle is healthy. What is the probability that the healthy uncle is heterozygous (Cc) if all of John's grandparents are healthy?

2/3

A condition in which one gene influences the phenotypic expression of another gene is called…

epistasis

If the allele Q is incompletely dominant over q, how many different phenotypes are present in the progeny of a cross between Qq and Qq individuals?

3

The trait of medium-sized leaves in iris is determined by the genotype PP'. Plants with large leaves are PP, whereas plants with small leaves are P'P'. A cross is made between two plants each with medium-sized leaves.

If they produce 80 offspring, what would be the expected number of offspring having large leaves?

20

For the cross AaBb x AaBb, if the genes assort independently, what fraction of the offspring would you expect to have the genotype Aabb?

2/16

In a disputed parentage case, the child is blood type O while the mother is blood type B. What blood type would exclude a male from being the father?

AB

Two fruit flies that are wingless are crossed, and it is discovered that all of their offspring have wings. This is an example of…

complementation

Two fruit flies that are wingless are crossed, and it is discovered that all of their offspring have wings.

For the two parent flies in question 33 above, the genetic mutations in the two flies most likely…

are in two different genes

With which of the following would hemizygosity most likely be associated?

x-linked inheritance

Which statement is true?

A. two genes on the same chromosome can assort independently from one another.

B. two genes on different chromosomes will assort independently from one another.

C. two genes close to each other on the same chromosome will probably not display independent assortment.

D. all of the other choices are correct.

D. all of the other choices are correct.

Assume that a test cross is made between AaBb and aabb plants and the phenotypes of offspring occur in the following numbers: 106 AB, 48 Ab, 52 aB, 94 ab. These results are consistent with…

linkage with approximately 33 map units between the two gene loci

Albinism in humans is inherited as a simple autosomal recessive trait. Two normal parents have five children and one is albino. If the parents have one more child, what is the probability that the child will not be albino?

A. 3/4

B. 1/4

C. 1/2

D. (3/4)^5

A. 3/4

In humans, the genetic basis for determining the sex “male” is accomplished by…

the presence of the SRY gene

A “Barr body” is…

an inactivated X chromosome, visible in the nucleus of a cell from a female mammal.

Which of the following statements is true?

All of the above:

For some organisms, sex is determined by a set of sex chromosomes.

For some organisms, females are diploid while males are haploid.

For some organisms, sex is determined by the temperature during embryonic development.

Assuming a person with pentaploidy could survive, a somatic cell from a person with pentaploidy would contain a total of how many chromosomes?

115

What is the expected number of Barr bodies in an individual with the karyotype XXXY?

2

The genotype XXY produces a…

female in Drosophila and a male in humans.

When an organism gains or loses one or more chromosomes but not a complete haploid set, the condition is known as…

aneuploidy

When a diploid organism gains a complete haploid set of chromosomes, the condition is known as…

triploidy

Hemophilia is caused by a sex-linked recessive gene. If a man with hemophilia marries a normal woman whose father had hemophilia, what is the probability that they will have a child who is both female and has hemophilia? (Note: in this problem you must include the probability of having a daughter in your computation of the final probability.)

1/4

The condition known as cri-du-chat syndrome in humans has a genetic constitution designated as…

46, 5p-

If an organism is heterozygous for a paracentric chromosomal inversion, then…

meiotic crossovers within the inverted region will not be recovered in offspring.

An abnormal chromosome in which the two arms of the chromosome are identical is called…

an isochromosome

Diseases associated with “genetic anticipation” are often caused by…

expansion of trinucleotide repeats.

The fact that a fly that is homozygous for bar-eye has a different of phenotype than a fly that is heterozygous for a double-bar and a wild type allele can be explained by:

positon effect

Which statement is most accurate regarding trisomy 21?

None of the other statements is correct.:

It always involves a nondisjunction inherited from mom

It usually involves a nondisjunction inherited from dad.

Most cases are familial.

Forms of inheritance that do not follow typical Mendelian patterns and that appear to be more influenced by the parent contributing the most cytoplasm to the embryo are most appropriately grouped under the general heading of…

extranuclear inheritance

In the snail Lymnaea peregra, the pattern of shell coiling is determined by the genotype of the egg-producing parent regardless of the phenotype of that parent. This type of inheritance is best referred to as:

maternal effect, or maternal influence

The terms “spindle transfer” and “pronuclear transfer” are two processes involved in…

producing “three-parent” babies

Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in prokaryotes and eukaryotes?

Double-stranded, antiparallel, (A+T)/(C+G)=variable, (A+G)/(C+T)=1.0

The arrow labeled “I” is pointing to the backbone of the helix. The backbone of the helix is made of:

sugars and phosphates

If the arrow labeled “III” is pointing to a pyrimidine named “C” then the arrow labeled “II” is pointing to:

a purine named “G”

If item III is a pyrimidine named “T” then the items labeled “II” and “III” are held together (to each other) by…

two hydrogen bonds.

The fact that there is a problem maintaining the very ends of eukaryotic chromosomes during replication has to do with…

the inability of DNA polymerases to initiate synthesis without an RNA primer.

Which statement is true?

None of the above.:

All DNA has the structure of “B DNA” all of the time.

DNA is always in the form of a right-handed helix.

Structurally, the two strands of DNA in a helix have the same polarity.

The enzyme that appears to be inappropriately expressed in at least some cancer cells and helps to maintain the very ends of eukaryotic chromosomes is called…

telomerase

Chromatin of eukaryotes is organized into repeating interactions with protein octamers called nucleosomes. Nucleosomes contain which class of protein molecules?

histones

Merck's anti-COVID-19 pill known as molnupiravir is a ribonucleotide analog that gets incorporated into the SARS-CoV-2 genome and rapidly tatutomerizes. Molnupiravir likely induces high levels of what type of event in the viral genome?

point mutations

Microsatellite DNA sequences…

are present in eukaryote genomes as tandem repeats of a very short sequence

In a transversion mutation,…

a pyrimidine substitutes for a purine.

During mismatch repair in bacteria, the newly synthesized strand is distinguished from the old strand by…

methylation on the old strand.

Liza, the very ambitious student, has a good friend named Alannah. Alannah was wondering what the first step in base excision repair is. You want to help out Alannah so you tell her that the first step in base excision repair is...

a base removed by the action of a DNA glycosylase.

Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing dimers at normal rates. Such individuals are likely to suffer from…

skin cancer

A somatic cell from a triploid person contains how many centromeres during the G1 phase of the cell cycle?

69

A balanced translocation…

leads to the condition of “semisterility” even in the absence of any crossing-over.

If an organism is heterozygous for a chromosomal inversion, then

meiotic crossovers within the inverted interval are not recovered in offspring.

Familial Down syndrome is caused by:

a centric fusion.

A fertilized egg inherited one X and one Y chromosome, but after several rounds of cell division in the embryo a cell is produced that has lost the Y chromosome. Which of the following is a possibility regarding the individual that develops from this embryo?

each of the other choices is possible: the person is a hermaphrodite. the person displays the characteristics of Turner Syndrome. the person may have little or no phenotype.