Ch9

A

A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring. A) heterozygous for the trait and able B) heterozygous for the trait and unable C) homozygous for the trait and able D) homozygous for the trait and unable

C

A colorblind woman marries a man who is not colorblind. All of their sons, but none of their daughters, are colorblind. Which of the following statements correctly explains these results? A) The gene for color vision is incompletely dominant to the gene for sex determination. B) The gene for color vision is codominant with the gene for sex determination. C) The gene for color vision is found on the X chromosome. D) The gene for color vision is found on the Y chromosome.

C

A monohybrid cross is A) the second generation of a self-fertilized plant. B) a breeding experiment in which the parental varieties have only one trait in common. C) a breeding experiment in which the parental varieties differ in only one character. D) a breeding experiment in which the parental varieties have only one prominent trait.

B

A person with AB blood illustrates the principle of A) incomplete dominance. B) codominance. C) pleiotropy. D) polygenic inheritance.

A

A testcross is A) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest. B) a mating between an individual of unknown genotype and an individual heterozygous for the trait of interest. C) a mating between two individuals heterozygous for the trait of interest. D) a mating between two individuals of unknown genotype.

B

According to scientists, about what percentage of men currently living in Central Asia may be descended from the Mongolian ruler Genghis Khan? A) 4% B) 8% C) 25% D) 40%

B

All the offspring of a cross between a black-eyed Mendelian and an orange-eyed Mendelian have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed Mendelian? A) 3 black-eyed:1 orange-eyed B) 0 black-eyed:1 orange-eyed C) 1 black-eyed:3 orange-eyed D) 1 black-eyed:0 orange-eyed

C

All the offspring of a cross between a red-flowered plant and a white-flowered plant have pink flowers. This means that the allele for red flowers is ________ to the allele for white flowers. A) dominant B) codominant C) incompletely dominant D) recessive

C

Amniocentesis and chorionic villus sampling allow for ________ and ________ of the fetus so that it can be tested for abnormalities. A) imaging; karyotyping B) sexing; imaging C) karyotyping; biochemical testing D) direct observation; biochemical testing

B

Any gene located on a sex chromosome A) is called a recessive gene. B) is called a sex-linked gene. C) will exhibit pleiotropy. D) will exhibit codominance.

B

Assuming that the probability of having a female child is 50% and the probability of having a male child is also 50%, what is the probability that a couple's first-born child will be female and that their second-born child will be male? A) 20% B) 25% C) 50% D) 75%

B

Below are two statements. Which (if any) applies to the law of segregation? Which (if any) applies to the law of independent assortment? I: Phenotypes for long tails and big eyes are inherited separately in lab mice. II: A baby mouse inherits a maternal red eye allele and a paternal black eye allele. A) A: segregation; B: independent assortment B) A: independent assortment; B: segregation C) A: segregation; B: segregation D) A: independent assortment; B: independent assortment

C

Blood samples are taken from the heel of newborn babies to test for a mutation in the PKU gene, which, if left untreated and in severe cases, can lead to mental retardation, reduced skin pigmentation, and seizures. Which concept is being illustrated by this example? A) incomplete dominance B) polygenic inheritance C) pleiotropy D) codominance

B

Crossing over ________ genes into assortments of ________ not found in the parents. A) recombines unlinked; genes B) recombines linked; alleles C) combines unlinked; alleles D) combines linked; genes

C

Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes? A) DD and dd B) dd and dd C) Dd and Dd D) Dd and DD

C

Female inheritance patterns cannot be analyzed by simply studying the X chromosome because A) the X chromosome is too large to analyze effectively. B) the X chromosome sometimes exchanges genetic information with the Y chromosome. C) the X chromosome is obtained from both father and mother. D) one X chromosome is deactivated in females.

A

For most sexually reproducing organisms, Mendel's laws A) cannot strictly account for the patterns of inheritance of many traits. B) explain the biological mechanisms behind why certain genes are dominant or recessive. C) help us understand the global geographic patterns of genetic disease. D) can predict whether offspring will be male or female with 100% accuracy.

C

Genes located close together on the same chromosomes are referred to as ________ genes and generally ________. A) linked; sort independently during meiosis B) homologous; are inherited together C) linked; do not sort independently during meiosis D) codependent; do not sort independently during meiosis

A

Given the sex determination system in bees, we can expect that A) female bees will produce eggs by meiosis, whereas male bees will produce sperm by mitosis. B) female bees will produce eggs by mitosis, whereas male bees will produce sperm by meiosis. C) male and female bees will produce sperm and eggs by meiosis. D) male and female bees will produce sperm and eggs by mitosis.

C

How is sex determined in most ants and bees? A) by the X-Y system B) by the Z-W system C) by the number of chromosomes D) by the size of the sex chromosome

A

How many sex chromosomes are in a human gamete? A) one B) two C) three D) four

D

If A is dominant to a and B is dominant to b, what is the expected phenotypic ratio of the cross AaBb × AaBb? A) 16:0:0:0 B) 8:4:2:2 C) 1:1:1:1 D) 9:3:3:1

A

If independent assortment did not occur, which of the following would be true? A) Genes for two different traits would be inherited together as a pair. B) Meiosis II would not be required to produce gametes, as meiosis I would be sufficient. C) A dihybrid cross of heterozygous individuals would yield four different phenotypes. D) Each sperm and egg would carry more than one allele for a specific gene.

A

Imagine that beak color in a finch species is controlled by a single gene. You mate a finch homozygous for orange (pigmented) beak with a finch homozygous for ivory (unpigmented) beak and get numerous offspring, all of which have a pale, ivory-orange beak. This pattern of color expression is most likely to be an example of A) incomplete dominance. B) codominance. C) pleiotropy. D) polygenic inheritance

C

Imagine that we mate two black Labrador dogs with normal vision and find that three of the puppies are like the parents, but one puppy is chocolate with normal vision and another is black with PRA (progressive retinal atrophy, a serious disease of vision). We can conclude that A) both of the parents are homozygous for both traits. B) the same alleles that control coat color can also cause PRA. C) the alleles for color and vision segregate independently during gamete formation. D) the alleles for color and vision segregate dependently during gamete formation.

A

In giraffes, long necks (N), long legs (L), dark spots (D), and the ability to digest meat (M) are all dominant traits. What possible genotype could a long-necked, short-legged, light-spotted, meat-digesting giraffe have? A) NnllddMM B) NNLLDdMm C) NNllddmm D) nnLLddMM

A

Linked genes generally A) do not follow the laws of independent assortment. B) show incomplete dominance. C) reflect a pattern of codominance. D) show pleiotropy

A

Mendel conducted his most memorable experiments on A) peas. B) roses. C) guinea pigs. D) fruit flies.

C

Mendel's law of independent assortment states that A) chromosomes sort independently of each other during mitosis and meiosis. B) independent sorting of genes produces polyploid plants under some circumstances. C) each pair of alleles segregates independently of the other pairs of alleles during gamete formation. D) genes are sorted concurrently during gamete formation.

B

Most genetic disorders of humans are caused by A) multiple alleles. B) recessive alleles. C) a mutation that occurs in the egg, sperm, or zygote. D) dominant alleles.

B

Most people afflicted with recessive disorders are born to parents who were A) both affected by the disease. B) not affected at all by the disease. C) slightly affected by the disease, showing some but not all of the symptoms. D) subjected to some environmental toxin that caused the disease in their children

B

Recessive X-linked traits are more likely to be expressed in a male fruit fly than a female fruit fly because A) males are haploid. B) the male's phenotype results entirely from his single X-linked gene. C) the male chromosome is more fragile than the female chromosome. D) the male chromosome is more susceptible to mutations.

B

Research since Mendel's time has established that the law of segregation of genes during gamete formation A) applies to all forms of life. B) applies to all sexually reproducing organisms. C) applies to all asexually reproducing organisms. D) is invalid.

B

Sex-linked conditions are more common in men than in women because A) men acquire two copies of the defective gene during fertilization. B) men need to inherit only one copy of the recessive allele for the condition to be fully expressed. C) the sex chromosomes are more active in men than in women. D) the genes associated with the sex-linked conditions are linked to the Y chromosome, which determines maleness

A

Sickle-cell disease is an example of A) codominance and pleiotropy. B) multiple alleles, pleiotropy, and blended inheritance. C) codominance and multiple alleles. D) multiple alleles and pleiotropy.

D

The alleles of a gene are found at ________ chromosomes. A) the same locus on nonhomologous B) different loci on homologous C) different loci on nonhomologous D) the same locus on homologous

B

The chromosome theory of inheritance states that A) chromosomes that exhibit mutations are the source of genetic variation. B) the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance. C) the behavior of chromosomes during mitosis accounts for inheritance patterns. D) humans have 46 chromosomes.

B

The expression of both alleles for a trait in a heterozygous individual illustrates A) incomplete dominance. B) codominance. C) pleiotropy. D) polygenic inheritance

D

The individual features of all organisms are the result of A) genetics. B) the environment. C) the environment and individual needs. D) genetics and the environment. Answer: D

D

The mechanism that "breaks" the linkage between linked genes is A) pleiotropy. B) codominance. C) independent assortment. D) crossing over

D

The phenotypic ratio resulting from a dihybrid cross of two heterozygote individuals showing independent assortment is expected to be A) 1:2:1 B) 3:1 C) 9:1:1:3 D) 9:3:3:1

B

The sex chromosome complement of a normal human female is A) XO. B) XX. C) XY. D) YY.

B

Using a six-sided die, what is the probability of rolling either a 5 or a 6? A) 1/6 × 1/6 = 1/36 B) 1/6 + 1/6 = 1/3 C) 1/6 + 1/6 = 2/3 D) 1/6

D

Varieties of plants in which self-fertilization produces offspring that are identical to the parents are referred to as A) hybrids. B) the F2 generation. C) monohybrid crosses. D) true-breeding.

C

What is meant by the statement that "male bees are fatherless"? A) Male bees don't play a role in the rearing of bee young. B) Male bees are produced by budding. C) Male bees develop from unfertilized eggs. D) The queen bee's mate dies before the male eggs hatch.

C

What is the normal complement of sex chromosomes in a human male? A) two Y chromosomes B) two X chromosomes and one Y chromosome C) one X chromosome and one Y chromosome D) one Y chromosome

B

Which of the following is an example of incomplete dominance in humans? A) albinism B) hypercholesterolemia C) skin color D) ABO blood groups

D

Which of the following is essentially the opposite of pleiotropy? A) incomplete dominance B) codominance C) multiple alleles D) polygenic inheritance

D

Which of the following kinds of data could be used to map the relative position of three genes on a chromosome? A) the frequencies with which the genes exhibit incomplete dominance over each other B) the frequencies of mutations in the genes C) the frequencies with which the genes are inherited from the mother and from the father D) the frequencies with which the corresponding traits occur together in offspring

C

Which of the following statements best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders? A) Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles. B) Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause the death of the embryo. C) Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce. D) The presence of a lethal dominant allele causes sterility.

B

Which of the following statements best represents the theory of pangenesis developed by Hippocrates? A) Pregnancy is a spontaneous event, and the characteristics of the offspring are determined by the gods. B) Particles called pangenes, which originate in each part of an organism's body, collect in the sperm or eggs and are passed on to the next generation. C) Offspring inherit the traits of either the mother or the father, but not both. D) Heritable traits are influenced by the environment and the behaviors of the parents.

A

Which of the following statements is false? A) Incomplete dominance supports the blending hypothesis. B) The four blood types result from various combinations of the three different ABO alleles. C) ABO blood groups can provide evidence of paternity. D) The impact of a single gene on more than one character is called pleiotropy.

C

Which of the following statements regarding cross-breeding and hybridization is false? A) The offspring of two different varieties are called hybrids. B) The parental plants of a cross are the P generation. C) The hybrid offspring of a cross are the P1 generation. D) The hybrid offspring of an F1 cross are the F2 generation.

D

Which of the following statements regarding genetic testing is false? A) Genetic testing before birth requires the collection of fetal cells. B) Carrier testing helps determine whether a person carries a potentially harmful disorder. C) The screening of newborns can catch inherited disorders right after birth. D) Most human genetic diseases are treatable if caught early.

B

Which of the following statements regarding genotypes and phenotypes is false? A) The genetic makeup of an organism constitutes its genotype. B) An organism with two different alleles for a single trait is said to be homozygous for that trait. C) Alleles are alternate forms of a gene. D) The expressed physical traits of an organism are called its phenotype.

D

Which of the following statements regarding hypotheses about inheritance is false? A) The theory of pangenesis incorrectly suggests that reproductive cells receive particles from somatic cells. B) Contrary to the theory of pangenesis, somatic cells do not influence eggs or sperm. C) The blending hypothesis does not explain how traits that disappear in one generation can reappear in later generations. D) The blending hypothesis suggests that all of the traits of the offspring come from either the mother or the father.

B

Which of the following statements regarding prenatal testing is false? A) Results from chorionic villus sampling come faster than those from amniocentesis. B) Chorionic villus sampling is typically performed later in the pregnancy than amniocentesis. C) Ultrasound imaging has no known risk. D) Chorionic villus sampling and amniocentesis are usually reserved for pregnancies with higher than usual risks of complications.

B

Which of the following statements regarding sickle-cell disease is false? A) Persons who are heterozygous for sickle-cell disease are also resistant to malaria. B) Sickle-cell disease causes white blood cells to be sickle-shaped. C) All of the symptoms of sickle-cell disease result from the actions of just one allele. D) About one in 10 African Americans is a carrier of sickle-cell disease.

D

Which of the following terms refers to a situation where a single phenotypic character is determined by the additive effects of two or more genes? A) incomplete dominance B) codominance C) pleiotropy D) polygenic inheritance

C

You conduct a dihybrid cross. A ________ ratio would make you suspect that the genes are linked. A) 3:1 B) 1:1:1:1 C) 12:1:1:4 D) 9:3:3:1