Biology Practice Questions (Chapter 9)

4) 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 is female and second-born child is male? A) 25% B) 50% C) 100% D) 75% E) None of the choices are correct.

A) 25%

3) What is a testcross? A) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest B) a mating between two individuals heterozygous for the trait of interest C) a mating between an individual of unknown genotype and an individual heterozygous for the trait of interest D) a mating between an individual of unknown genotype and an individual homozygous dominant for the trait of interest E) None of the choices are correct.

A) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest

11) 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 corresponding traits occur together in offspring B) the frequencies with which the genes are inherited from the mother and from the father C) the frequencies with which the genes are heterozygous D) the frequencies of mutations in the genes E) the frequencies with which the genes exhibit incomplete dominance over each other

A) the frequencies with which the corresponding traits occur together in offspring

12) Why are sex-linked conditions more common in men than in women? A) Men acquire two copies of the defective gene during fertilization. B) Men need inherit only one copy of the recessive allele for the condition to be fully expressed. C) Women simply do not develop the disease regardless of their genetic composition. D) The sex chromosomes are more active in men than in women. E) None of the choices are correct.

B) Men need inherit only one copy of the recessive allele for the condition to be fully expressed.

10) In a cross of a purple-flowered, short-stemmed plant with a yellow-flowered, long-stemmed plant, the expected phenotypic ratio is 1 purple-short:1 purple-long:1 yellow-short:1 yellow-long. When you do the actual cross you observe a 5 purple-short:1 purple-long:1 yellow-short:5 yellow-long phenotypic ratio. Which of the following explains these results? A) The purple-long and yellow-short individuals are recombinants. B) The genes are linked. C) The relationship between the alleles involved in determining lining the phenotype is incomplete dominance.

B) The genes are linked.

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

B) is called a sex-linked gene.

2) Mendel's principle of independent assortment states that A) independent sorting of genes produces polyploid plants under some circumstances. B) genes sort independently of each other in animals but not in plants. C) each pair of alleles segregates independently during gamete fondation. D) chromosomes sort independently of each other during mitosis and meiosis. E) None of the choices are correct.

C) each pair of alleles segregates independently during gamete fonnation.

14) An animal species in which an individual produces both eggs and sperm is called A) monoecious. B) polyploid. C) hermaphroditic. D) pleiotropic. E) dioecious.

C) hermaphroditic.

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

C) one

6) 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 noimal 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 E) None of the choices are correct.

D) Dd and Dd

1) A monohybrid cross is A) a breeding experiment in which the parental varieties have only one trait in common. B) the second generation of a self-fertilized plant. C) a triploid plant that results from breeding two very different plants. D) a breeding experiment in which the parental varieties differ in only one trait. E) None of the choices are correct.

D) a breeding experiment in which the parental varieties differ in only one trait.

7) 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) crossing over. B) codominance. C) polygenic inheritance. D) incomplete dominance. E) pleiotropy.

D) incomplete dominance.

8) Which of the following best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders? A) The presence of a lethal dominant allele causes sterility. B) Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles. C) Many lethal recessive alleles cause enhanced disease resistance when they are present in the heterozygous state, and carriers of these alleles have more children, on average, than other people. D) Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause death of the embryo. E) 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.

E) 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.

5) A carrier of a genetic disorder who does not show symptoms is most likely to be to transmit it tooffspring. A) heterozygous for the trait and unable B) homozygous for the trait and able C) homozygous for the trait and unable D) None of the choices are correct. E) heterozygous for the trait and able

E) heterozygous for the trait and able

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

E) linked ... do not sort independently during meiosis