Genetics Exam 4

One map unit is equal to a recombination frequency of A) 1%. B) 10%. C) 100%. D) 5%. E) 50%.

A) 1%.

The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following? A) All of the genes controlling the traits behaved as if they were on different chromosomes. B) All of the genes controlling the traits were located on the same chromosome. C) The diploid number of chromosomes in the pea plants was 7. D) None of the traits obeyed the law of segregation. E) The formation of gametes in plants occurs by mitosis only.

A) All of the genes controlling the traits behaved as if they were on different chromosomes.

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants? A) Traits are inherited in discrete units, and are not the results of "blending." B) Recessive genes occur more frequently in the F1 generation than do dominant ones. C) Genes are composed of DNA. D) An organism that is homozygous for many recessive traits is at a disadvantage. E) There is considerable genetic variation in garden peas.

A) Traits are inherited in discrete units, and are not the results of "blending."

A condition in which one gene pair masks the expression of a nonallelic gene pair is called________. A) epistasis B) codominance C) additive alleles D) dominance E) recessiveness

A) epistasis

How many possible gametes can be produced by a short plant with yellow, round peas with a heterozygous genotype (YyRrSs)? A: 8 B: 6 C: 12 D: 3 E: 10

A: 8

Assuming independent assortment, what phenotypic ratio would you expect to see if an individual with the genotype RrGg is self-crossed? A: 9:3:3:1 B: 3:1 C: 1:2:1 D: 1:3:2:1 E: 1:3

A: 9:3:3:1

A situation in which there are more than two alternative forms of a given gene would be call ______________. A: Multiple alleles B: hemizygosity C: codominance D: incomplete dominance E: alternation of generations

A: Multiple alleles

Expression of ______ would inhibit X-inactivation. A: TsiX B: Xic C: Xist D: All of the answers are correct E: none of the answers are correct

A: TsiX

What dosage compensation mechanism is employed by female placental mammals? A: X-inactivation B: Y-inactivation C: synteny D: X chromosome E: X nondisjunction

A: X-inactivation

The law of segregation states that the F2 progeny of F1 heterozygous plants will exhibit A: a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio B: a 9:3:3:1 phenotypic ratio and 1:2:1 C: a 1:2:1 phenotypic ratio and a 1:2:1 genotypic ration D: a 3:1 phenoypic ratio and a 3:1 genotypic ration E: a 9:3:3:1 phenotypic ratio and 9:3:3:1 genotypic ratio

A: a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason? A: different possible alignments of chromosomes B: the tendency for dominate alleles to segregate together C: recurrent mutations forming new alleles D: crossing over during prophase I

A: different possible alignments of chromosomes

Two proteins interact to form a multimeric complex. When one of the proteins is mutated, there is a substantial loss of functional activity in the multimeric protein. This type of mutation is classified as A: dominant-negative B: hypomorphic C: hypermorphic D: neomorphic E: amorphic

A: dominant-negative

Gene interactions in which an allele of one gene modifies or prevents expression of alleles of another gene is known as A: epistasis B: codominance C: incomplete penetrance D: incomplete dominance E: complete dominance

A: epistasis

Which of the following organelles are involved in the general category of organelle heredity? A: mitochondria and chloroplast B: lysosomes and peroxisomes C: Golgi and the endoplasmic reticulum D: Golgi and nuclei E: F factors and episomes

A: mitochondria and chloroplast

During meiosis I, when does homologous chromosome pairing and recombination occur? A: prophase I B: telophase I C: metaphase I D: anaphase I E: prometaphase I

A: prophase I

Mendel performed many types of crosses, including those in which the same genotypes are crossed but the sexes of the parents are switched. These are known as A: reciprocal crosses B: replicate crosses C: monohybrid crosses D: dihybrid crosses E: test crosses

A: reciprocal crosses

With incomplete dominance, a likely ratio resulting from a monohybrid cross would be________. A) 3:1 B) 1:2:1 C) 9:3:3:1 D) 1:2:2:4 E) 3:3

B) 1:2:1

Manx cats have no tails. When two Manx cats are bred together there is always a one third chance that a kitten will have a tail. When a Manx cat is bred to a cat with a normal tail there is a one-half chance that a kitten will have a tail. Which of the following is the best explanation for this? A) The Manx genotype exhibits variable expression. B) The Manx phenotype is dominant, but the allele is a recessive lethal. C) The Manx phenotype is a result of heteroplasmy. D) The Manx phenotype is caused by gene interactions. E) The Manx phenotype is dominant epistatic.

B) The Manx phenotype is dominant, but the allele is a recessive lethal.

Mendel's second law of independent assortment has its basis in which of the following events of meiosis I? A) crossing over B) alignment of tetrads at the equator C) synapsis of homologous chromosomes D) separation of homologs at anaphase E) separation of cells at telophase

B) alignment of tetrads at the equator

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason? A) recurrent mutations forming new alleles B) different possible alignments of chromosomes C) crossing over during prophase I D) segregation of maternal and paternal alleles E) the tendency for dominant alleles to segregate together

B) different possible alignments of chromosomes

The closer together two genes are on a chromosome, A) the more likely there will be a recombination event between them. B) the less likely there will be a recombination event between them. C) the more likely they are to be epistatic. D) the greater the chance that a double crossover will occur between them. E) the less likely they are to be good genetic markers.

B) the less likely there will be a recombination event between them.

A couple has four children. What is the probability that they would have four boys? A: 1/32 B: 1/16 C: 1/8 D: 1/4 E: 1/2

B: 1/16

Who originally identified a highly condensed structure in the interphase of nuclei? A: Ohno B: Barr C: Lyon D: None of the answers are correct

B: Barr

Individuals with an XXY karyotype are ________ in humans and _______ in fruit flies. A: male, male B: male, female C: female, male D: female, female E: male, intersexual

B: male, female

The alleles of linked genes tend to A: be mutated more often than unlinked genes B: segregate together during gamete production C: assort independently and show a higher rate of crossing D: experience a higher rate of crossing over

B: segregate together during gamete production

The diploid cell formed by the fertilization of the egg by sperm during sexual reproduction is a A: reciprocal B: zygote C: dihybrid D: gamete E: monohybrid

B: zygote

8) A couple with three girls is expecting a fourth child. The probability that this child is also a girl is A) 0 B) 1/16 C) 1/2 D) 1/8 E) 1/32

C) 1/2

Phenotypically, a female (XX) mouse embryo that was transformed with a small piece of a Y chromosome bearing the SRY gene would develop as A) a male initially, then revert to female after birth. B) a female. C) a male. D) a female initially, then revert to male after birth. E) an intersex individual.

C) a male.

Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this? A) epistasis B) incomplete dominance C) pleiotropy D) codominance E) multiple alleles

C) pleiotropy

Which of the following is an example of polygenic inheritance? A) the ABO blood group in humans B) Huntington's disease in humans C) skin pigmentation in humans D) white and purple flower color in peas E) pink flowers in snapdragons

C) skin pigmentation in humans

Typical ratios resulting from epistatic interactions in dihybrid crosses would be ________. A: 1:2:2:4:1:2:1:2:1 B: 3:1, 1:1 C: 9:3:4, 9:7 D: 9:3:3:1, 1:21

C: 9:3:4, 9:7

In humans, the genetic basis for determining the sex "male" is accomplished by the presences of ___________. A: one X chromosome B: a balance between the number of X chromosomes and the number of haploid sets of autosomes C: a portion of the Y chromosome D: multiple alleles scattered throughout the autosomes E: high levels of estrogen

C: a portion of the Y chromosome

In human blood groups, the fact that an individual can have an AB blood type is an example of ________. A: incomplete dominance B: incomplete penetrance C: codominance D: sex-influenced trait E: temperature-sensitive conditional allele

C: codominance

Most people with the dominant mutant polydactyly allele have extra digits, but at least 25% have the normal number of digits. What is the genetic explanation for this observation? A: Partial dominance B: temperature-sensitive allele C: incomplete dominance D: dominant-negative allele

C: incomplete dominance

Which mode of inheritance produces heterozygotes with a phenotype that different from either homozygote but more closely resembles one homozygous phenotype than the other? A: epistasis B: incomplete penetrance C: incomplete dominance D: complete dominance E: codominace

C: incomplete dominance

Huntington disease in humans is an example of ________. A: semilethal alleles B: epistasis C: lethal alleles D: recessive inheritance E: environmental effects

C: lethal alleles

For a certain trait, a heterozygous individual has a selective advantage as compared to a homozygous dominant or homozygous recessive individual. This is called ________. A: codominance B: multiple allele systems C: overdominance D: incomplete penetrance E: incomplete dominance

C: overdominance

If an allele is dominant in one sex and recessive in another, it is an example of ________. A: sex-limited inheritance B: incomplete dominance C: sex-influenced inheritance D: simple Mendelian inheritance

C: sex-influenced inheritance

A physical exchange of chromosome pieces that most commonly occurs during prophase of meiosis I.

Crossing over

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 crosses BbTt × BBtt will be expected to have black fur and long tails? A) 9/16 B) 3/16 C) 1/16 D) 1/2 E) 3/8

D) 1/2

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white -eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? A) The gene involved is on the Y chromosome. B) Other female-specific factors influence eye color in flies. C) Other male-specific factors influence eye color in flies. D) The gene involved is on the X chromosome. E) The gene involved is on an autosome, but only in males.

D) The gene involved is on the X chromosome.

Crossing-over is A) an extremely rare event. B) an event that only takes place during meiosis. C) the place on a homologous pair of chromosomes at which a physical exchange occurs. D) the reciprocal exchange of homologous regions of chromatids. E) not useful in mapping genes.

D) the reciprocal exchange of homologous regions of chromatids.

Among the dihybrid crosses below, which will produce a 1:1 phenotypic ratio? A: AABB x aabb B: AaBb x AaBb C: AaBb x aabb D: AaBB x aaBB E: AAbb x aaBB

D: AaBB x aaBB

In Drosophilia, A: Females are XX, and males are XY or XO B: Females XY, and males are XX C: Females are XX or XO, and males are XY or XXY D: Females are XX or XXX, and males are XY or XO E: Females are XX or XXX, and males are XY or XXY

D: Females are XX or XXX, and males are XY or XO

Which of the following is primarily responsible for the maternal effect? A: Oocytes B: Placenta C: Sperm cells D: Nurse cells

D: Nurse cells

Morgan's analysis of a white-eyed male Drosophila mutation helped explain A: independent assortment B: random assortment C: crossing over D: X-linked inheritance E: autosomal domiance

D: X-linked inheritance

What is the genotype for individuals with blood type O? A: I^Bi B: I^AIB C: I^Ai D: ii E: either I^Ai or I^Bi

D: ii

Which of the following is an example of polygenic inheritance? A: the ABO blood group in humans B: Huntington's disease in humans C: pink flowers in snapdragons D: skin pigmentation in humans

D: skin pigmentation in humans

Describes an allele that determines the phenotype of a heterozygote.

Dominant

In a pea plant that is heterozygous for seed color, what proportion of gametes will carry the recessive allele? A) 1/6 B) 1/4 C) 3/4 D) 1/8 E) 1/2

E) 1/2

A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their next offspring would be expected to have normal pigmentation? A) about 90% B) 50% C) about 66% D) 25% E) 75%

E) 75%

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties? A) The traits blended together during fertilization. B) No genes interacted to produce the parental phenotype. C) Different genes interacted to produce the parental phenotype. D) Each allele affected phenotypic expression. E) One phenotype was completely dominant over another.

E) One phenotype was completely dominant over another.

Individuals with Turner syndrome are A) haploid. B) euploid. C) monoploid. D) polyploid. E) aneuploid.

E) aneuploid.

The actual alleles present in an individual make up the individual's A: recombinant types B: zygote C: dominate alleles D: allele E: genotype

E: genotype

Direction of shell coiling in the snail Limnaea peregra is conditioned by a form of extrachromosomal inheritance known as ________. A: heteroplasmy B: epistasis C: sex-linked inheritance D: independent assortment E: maternal effect

E: maternal effect

A region that influences the choice of the X chromosome during the process of X inactivation.

Xce

In those species with two types of sex chromosomes, the sex produces two types of gametes.

hetrogametic

A cross in which the outcomes of only one single trait are followed.

monohybrid cross