Biology 171 Chapter 10

A ________ trait is one that can be passed from one generation to another.

A ________ is a portion of DNA that resides at a particular locus or site on a

chromosome and encodes a particular function.

To determine the overall probability of independent events, ________ the probabilities of

the individual events.

One particular allele of a gene may be defined as ________ or standard, because it is present in most individuals and gives rise to an expected trait, or phenotype.

Geneticists make use of ________ frequencies to map chromosomes, that is, to locate

genetic loci on the chromosome.

A cross between two parents that differs by a single trait is a ________ cross.

The physical appearance of a character is the ________, while the genetic constitution is

the ________.

A cross between two parents that differs by two independent traits is a ________ cross.

For genes that fail to independently assort, phenotypes that appear in combinations that

are not present in either parent are ________.

The region of a chromosome occupied by a gene is called a ___________.

When a cross is made and a trait disappears in the F1 generation, only to reappear in the F2, the trait is probably ___________.

A female who is heterozygous for a recessive, sex-linked character is a _______________.

When the expression of one gene depends on the expression of another gene, the genes demonstrate _______________.

When many genes contribute to the phenotype, variation is said to be __________.

A ________ is a feature, such as flower color; a ________ is a particular form of a

character, such as a white flower.

Gregor Mendel presented his genetics project orally in A) 1565 B) 1665 C) 1765 D) 1865 E) 1965

Mendel concluded that each pea has two units for each character, and each gamete

contains one unit. Mendel's "unit" is now referred to as a(n)

A) gene. B) character. C) allele. D) transcription factor. E) None of the above

A particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait is referred to as a A) parental cross. B) dihybrid cross. C) filial generation mating. D) reciprocal cross. E) test cross.

Incomplete dominance occurs when A) chromosomes are deleted. B) heterozygotes synthesize a reduced amount of an enzyme, producing an intermediate

phenotype. C) the genes fail to segregate. D) the law of independent assortment is upheld. E) one gene is epistatic to the other.

Although the law of independent assortment is generally applicable, when two loci are on the same chromosome the phenotypes of the progeny sometimes do not fit the phenotypes predicted. This is due to A) translocation B) inversions C) chromatid affinities D) linkage E) reciprocal chromosomal exchanges.

When a given trait is the result of multigene action, one of the genes may mask the

expression of one or all other genes. This phenomenon is termed

A) epistasis. B) epigenesis. C) dominance. D) incomplete dominance. E) None of the above

Which of the following is not a characteristic that makes an organism suitable for genetic

studies?

A) A small number of chromosomes B) A short generation time C) Ease of cultivation D) The ability to control crosses E) The availability of a variation for traits

A key factor that allowed Mendel to interpret his breeding experiments was that A) the varieties of peas he started with were "true-breeding." B) peas naturally self-pollinate. C) peas can reproduce asexually. D) pollination could be controlled. E) a and d

Crossing spherical-seeded pea plants with wrinkled-seeded pea plants resulted in progeny

that all had spherical seeds. This indicates that the wrinkled-seed trait is

A) codominant. B) dominant. C) recessive. D) a and b E) a and c

Imaginary schmoos live in geographically separated groups and rarely interbreed. On one occasion, two from the different groups did mate. A big-footed white schmoo mated with a small-footed brown schmoo. Three offspring resulted: one big-footed brown schmoo and two small-footed brown schmoos. Which statement about the inheritance of color in schmoos is most likely to be correct? A) Brown is dominant to white. B) White is dominant to brown. C) White and brown are codominant. D) a and c E) You cannot reach any conclusions.

Which statement about the inheritance of footedness in schmoos is most likely to be

correct?

A) Big is dominant to small. B) Small is dominant to big. C) Big and small are codominant. D) a and c E) You cannot reach any conclusions.

If big feet (B) in schmoos is dominant to small feet (b), what is the genotype of the big-

footed white parent schmoo with respect to the foot gene?

A) bb B) BB C) Bb D) a and b E) a and c

When reciprocal crosses produce identical results, the trait is A) sex-linked. B) not sex-linked. C) not autosomally inherited. D) a and b E) b and c

The physical appearance of a character is called A) the genotype. B) the phenotype. C) an allele. D) a trait. E) a gene.

Different forms of a gene are called A) traits. B) phenotypes. C) genotypes. D) alleles. E) None of the above

When genes for two different characters segregate in a cross, what type of cross is it? A) Monohybrid B) Dihybrid C) Trihybrid D) F1
E) F2

In Mendel's experiments, if the allele for tall (T) plants was incompletely dominant over the allele for short (t) plants, what would be the result of crossing two Tt plants? A) 1/4 would be tall; 1/2 intermediate height; 1/4 short. B) 1/2 would be tall; 1/4 intermediate height; 1/4 short. C) 1/4 would be tall; 1/4 intermediate height; 1/2 short. D) All the offspring would be tall. E) All the offspring would be intermediate.

The region of the chromosome occupied by a gene is called a(n) A) allele. B) region. C) locus. D) type. E) phenotype.

In Mendel's experiments, the spherical seed character (SS) is completely dominant over the wrinkled seed character (ss). If the characters for height were incompletely dominant, such that TT are tall, Tt are intermediate, and tt are short, what would be the result of crossing a spherical-seeded, short (SStt) plant to a wrinkled-seeded, tall (ssTT) plant? A) 1/2 would be smooth-seeded and intermediate height; 1/2 would be smooth-seeded

and tall.

B) All the progeny would be smooth-seeded and tall. C) All the progeny would be smooth-seeded and short. D) All the progeny would be smooth-seeded and intermediate height. E) You cannot predict the outcome.

If Mendel's crosses between spherical-seeded tall plants and wrinkled-seeded short plants had produced many more than 1/16 wrinkled-seeded short plants in the F2 generation, he

might have concluded that

A) the spherical seed and tall traits are linked. B) the wrinkled seed and short traits are unlinked. C) all traits in peas assort independently of each other. D) all traits in peas are linked. E) He would not have concluded any of the above.

At a certain locus of the human genome, it is found that 200 different alleles exist in the

population. Each person would have at the most __________ alleles.

A) 1 B) 2 C) 100 D) 200 E) 400

An organism that produces either male gametes or female gametes, but not both, is called A) monoecious. B) dioecious. C) heterozygous. D) homozygous. E) parthenogenic.

Why would you predict that half of the human babies born will be males and half will be

females?

A) Because of the segregation of the X and Y chromosomes during male meiosis B) Because of the segregation of the X chromosomes during female meiosis C) Because all eggs contain an X chromosome D) a and b E) a and c

A human male carrying an allele for a trait on the X chromosome is A) heterozygous. B) homozygous. C) hemizygous. D) monozygous. E) holozygous.

Cleft chin is a sex-linked dominant trait. A man with a cleft chin marries a woman with a round chin. What proportion of their female progeny will show the trait? A) 0% B) 25% C) 50% D) 75% E) 100%

Cleft chin is a sex-linked dominant trait. A man with a cleft chin marries a woman with a round chin. What proportion of their male progeny will show the trait? A) 0% B) 25% C) 50% D) 75% E) 100%

A linkage group corresponds to A) a group of genes on different chromosomes. B) the linear order of chromomeres on a chromosome. C) the length of a chromosome. D) a group of genes on the same chromosome. E) None of the above

It would have been very difficult for Mendel to draw conclusions about the patterns of

inheritance if he had used cattle instead of peas. Why?

A) Cattle reproduce asexually. B) Cattle have small numbers of offspring. C) Cattle do not have observable phenotypes. D) Cattle do not have genotypes. E) Cattle do not have autosomes.

Epistasis refers to A) a group of genes that are close together. B) the interaction of two genes so that a new phenotype is produced. C) the expression of two genes in the same individual. D) the linear order of genes on a chromosome. E) the expression of one gene masking the expression of another.

An agouti mouse that is heterozygous at the agouti and albino loci (AaBb) is mated to an albino mouse that is heterozygous at the agouti locus (aaBb). (Non-albino mice without the dominant agouti allele are black.) What proportion of the progeny do you expect to be albino? A) 0% B) 12.5% C) 37.5% D) 50% E) 100%

An agouti mouse that is heterozygous at the agouti and albino loci (AaBb) is mated to an albino mouse that is heterozygous at the agouti locus (aaBb). (Non-albino mice without the dominant agouti allele are black.) What proportion of the progeny do you expect to be agouti? A) 0% B) 12.5% C) 37.5% D) 50% E) 100%

An agouti mouse that is heterozygous at the agouti and albino loci (AaBb) is mated to an albino mouse that is heterozygous at the agouti locus (aaBb). (Non-albino mice without the dominant agouti allele are black.) What proportion of the progeny do you expect to be black? Black is the alternate

phenotype to agouti.

A) 0% B) 12.5% C) 37.5% D) 50% E) 100%

The complete phenotype of an organism is dependent on A) genotype. B) penetrance. C) expressivity. D) polygenes. E) All of the above

When a dihybrid black, straight-winged fly is crossed to a double-recessive brown, curly-winged fly, the frequency at which black curly-winged and brown straight-winged flies

are seen in the progeny is called the

A) mutation frequency. B) mitotic frequency. C) meiotic frequency. D) allele frequency. E) recombinant frequency

Alleles for genes located on mitochondrial DNA are said to be maternally inherited. What

is the reason for this pattern of inheritance?

A) The egg and sperm contribute equal numbers of cytoplasmic organelles to the zygote. B) The egg contributes virtually all of the cytoplasmic organelles to the zygote. C) Half of the nuclear chromosomes in the zygote come from the father. D) Half of the nuclear chromosomes in the zygote come from the mother. E) All of the nuclear chromosomes in the zygote come from the mother.

Which of the following methods was not used by Mendel in his study of the genetics of

the garden pea?

A) Maintenance of true-breeding lines B) Cross-pollination C) Microscopy D) Production of hybrid plants E) Quantitative analysis of results

In Kˆlreuter's studies, reciprocal crosses A) always gave identical results. B) only involved heterozygous individuals. C) supported the blending hypothesis of inheritance. D) could only be done with homozygous individuals. E) consist of an F1 and an F2 generation.

Which of the following statements about Mendelian genetics is false? A) Alternate forms of genes are called alleles. B) A locus is a gene's location on its chromosome. C) Only two alleles can exist for a given gene. D) A genotype is a description of the alleles that represent an individual's genes. E) Individuals with the same phenotype can have different genotypes.

Segregation of alleles occurs A) during gamete formation. B) at fertilization. C) during mitosis. D) during the random combination of gametes to produce the F2 generation.
E) only in monohybrid crosses.

A pea plant with red flowers is test crossed, and one half of the resulting progeny have red flowers, while the other half have white flowers. You know that the genotype of the test-crossed parent was

A) RR. B) Rr. C) rr. D) either RR or Rr. E) You cannot tell unless the genotypes of both parents are known.

Which of the following phenomena cannot be observed using only dihybrid crosses? A) Crossing over B) Segregation of alleles C) Independent assortment of alleles D) Recessive lethal alleles E) None of the above

Separation of the alleles of a single gene into different gametes is called A) synapsis. B) segregation. C) independent assortment. D) heterozygous separation. E) recombination.

In mice, short hair is dominant to long hair. If a short-hair individual is crossed with a long-hair individual and both long- and short-hair offspring result, you can conclude that A) the short-hair individual was homozygous. B) the short-hair individual was heterozygous. C) the long-hair individual was homozygous. D) the long-hair individual was heterozygous. E) more offspring are required in order to decide the genotypes of the parents.