Bio. Ch.8 Test Review

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

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.

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.

A

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

A

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

A

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

A

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 Mendelians? 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

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

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

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) most genes associated with the sex-linked conditions are linked to the Y chromosome, which determines maleness.

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

B

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

B

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

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.

B

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

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

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

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 (chromosomes) segregates independently of the other pairs of alleles during gamete formation. D) genes are sorted concurrently during gamete formation.

C

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

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.

C

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

D

Justin has type A blood and his wife Brittany has type B blood. Justin's parents both have type AB blood, and Brittany's parents also both have type AB blood. What are the chances that Justin and Brittany's son Theodore has type A blood? A) 100% B) 75% C) 25% D) 0%

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

D

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

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.

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

D