Chapter 9 Sexual Reproduction and Meiosis

53) Genetic variability will not occur among offspring if crossing over does not occur during prophase I of meiosis. True or False

Answer: FALSE Explanation: Genetic variability also results from random fertilization and/or random orientation.

58) The roundworm Caenorhabditis elegans is a hermaphrodite and can only undergo sexual reproduction. True or False

Answer: FALSE Explanation: Hermaphrodite organisms can reproduce sexually or asexually.

46) Haploid germ cells undergo meiosis, including crossing over, to produce sex cells. True or False

Answer: FALSE Explanation: All of the statement is true except that germ cells are diploid.

47) Meiosis generates genetic variability by crossing over of homologous chromosomes in haploid somatic cells. True or False

Answer: FALSE Explanation: Crossing over does generate genetic variability, but it acts in diploid germ cells.

54) Genetic variability will not occur among offspring if random alignment does not occur during anaphase I of meiosis. True or False

Answer: FALSE Explanation: Genetic variability also results from crossing over.

45) If a human zygote has either 45 or 47 chromosomes it was caused by random fertilization. True or False

Answer: FALSE Explanation: Odd numbers of chromosomes result from nondisjunction in meiosis.

48) Identical twins result from a single fertilization to form a zygote, which then splits in half. True or False

Answer: TRUE Explanation: One zygote splitting involves no genetic change.

44) Mitosis occurs in somatic cells throughout life. True or False

Answer: TRUE Explanation: Somatic cells undergo mitosis to produce cells needed for growth and tissue repair.

27) Alternate forms of the same gene A) do not exist. B) are alleles. C) are homologs. D) are sister chromatids. E) do not occur in the same individual.

B) are alleles Explanation: Alleles are found at the same location on different homologous chromosomes and have somewhat different sequences.

33) People who have a single X chromosome are female, while those with XXY sex chromosomes are males. In order to be a female, a human A) must have two X chromosomes. B) cannot have a Y chromosome. C) must have only one X chromosome. D) must have only one Y chromosome. E) cannot have an X chromosome.

B) cannot have a Y chromosome. Explanation: Sex determination systems vary in different organisms; in humans, the Y chromosome must be absent for individuals to be female.

55) If you mate a donkey (2n = 62) with a horse (2n = 64) you get a mule. Mules are sterile and cannot produce gametes by meiosis because they A) contain too few chromosomes. B) have an odd number of chromosomes. C) have an even number of chromosomes. D) contain too many chromosomes. E) lack genes that are essential for life.

B) have an odd number of chromosomes. Explanation: Fertilization of gametes would yield an unmatched chromosome.

3) Sexual reproduction is important to the survival of a species in a changing environment because A) it requires less overall energy expenditure than asexual reproduction. B) it produces genetically different individuals. C) it requires only one individual. D) it produces genetically identical individuals. E) All answers are correct.

B) it produces genetically different individuals. Explanation: The new genetic combinations resulting from meiosis provide offspring which may be able to survive changes in the environment.

30) When chromosomes fail to separate during meiosis, this is known as A) crossing over. B) nondisjunction. C) translocation. D) random separation. E) mitosis.

B) nondisjunction. Explanation: Nondisjunction occurs when two copies of a chromosome fail to separate, resulting in gametes with one more or one less than the normal complement of chromosomes.

15) Meiotic cell division replicates a cell's DNA ________ and then divides ________. A) twice; once B) once; twice C) twice; twice D) once; once E) No answer is correct.

B) once; twice Explanation: By having only one replication but two divisions, meiosis reduces diploid germ cells to haploid sex cells.

43) If a diploid sperm fertilizes a diploid egg it will produce a ________ zygote. A) triploid B) tetraploid C) diploid D) haploid E) hexaploid

B) tetraploid Explanation: Two diploid gametes, if fused, give four sets of chromosomes to the zygote.

37) If a diploid cell goes through mitosis it will generate A) four haploid cells. B) two diploid cells. C) two haploid cells. D) four diploid cells. E) This is not possible.

B) two diploid cells. Explanation: Diploid cells produce diploid cells by mitosis since mitosis copies cells without altering their DNA content.

31) Nondisjunction may cause A) trisomy 21. B) Turner syndrome. C) Jacobs syndrome. D) Klinefelter syndrome. E) All answers are correct.

E) All answers are correct. Explanation: A number of genetic disorders result from nondisjunction and the imbalance of chromosomes that results.

2) Meiosis is a process that produces A) sperm cells. B) egg cells. C) gametes. D) haploid cells. E) All answers are correct.

E) All answers are correct. Explanation: The purpose of meiosis is to reduce cells to haploidy and to create new combinations of alleles.

50) Genetic information is passed from one generation to the next through A) DNA. B) asexual reproduction. C) sexual reproduction. D) gametes. E) All answers are correct.

E) All answers are correct. Explanation: There are many means by which genetic information passes from generation to generation, depending on the lifecycle of a particular organism.

36) If a haploid cell goes through meiosis it will generate A) four haploid cells. B) two diploid cells. C) two haploid cells. D) four diploid cells. E) No answer is correct.

E) No answer is correct. Explanation: Meiosis cannot start with a haploid cell since homologous pairs cannot be made, among other things.

40) Genes A and B are on the same chromosome. If a person has one chromosome with the alleles AB and a second chromosome with the alleles ab, how could they produce a gamete with a chromosome containing the alleles Ab or aB? A) independent assortment B) random fertilization C) mitosis D) fragmentation of the chromosome E) crossing over

E) crossing over Explanation: Crossing over allows for combinations on the same resulting chromosome from two different homologs.

8) If you were looking at a diagram of the male human body and were asked to locate the germ cells, you would point to the A) bone marrow. B) blood. C) brain. D) skin. E) testes.

E) testes. Explanation: Germ cells are used to produce the gametes.

11) The process that merges the gametes from two parents is A) fertilization. B) meiosis. C) mitosis. D) mutation. E) conjugation.

A) fertilization. Explanation: Fertilization restores the normal diploid number of chromosomes for a species.

16) Human diploid cells have A) 23 pairs of chromosomes. B) 23 chromosomes. C) 46 pairs of chromosomes. D) 2 pairs of sex chromosomes. E) 1 pair of autosomes.

A) 23 pairs of chromosomes. Explanation: Human diploid cells have one pair of sex chromosomes and twenty-two pairs of autosomes.

4) 2n is an abbreviation for A) diploid. B) gametes. C) haploid. D) mitosis. E) meiosis.

A) diploid. Explanation: In "2n,'' the '2' refers to the number of copies of chromosomes and the ''n'' refers to whole sets of chromosomes.

32) What is an advantage of sexual reproduction over asexual reproduction? A) genetic variability during an ecological disaster B) genetic variability when the environment is stable C) faster reproduction D) requirement of less energy E) simpler form of reproduction

A) genetic variability during an ecological disaster Explanation: The genetic variation generated by sexual reproduction provides a pool for adapting to changes and disasters in the environment. This has been long recognized by indigenous farmers and, more recently, by operators of seed banks.

7) 1n is an abbreviation for A) haploid. B) somatic cells. C) diploid. D) mitosis. E) meiosis.

A) haploid. Explanation: "1n" means that a cell has one copy of each chromosome for that species.

26) The process by which homologous chromosomes exchange genetic material A) is crossing over. B) is random fertilization. C) occurs only in bacteria. D) occurs only in animals. E) is independent assortment.

A) is crossing over. Explanation: The process of genetic exchange during meiosis is called "crossing over" because DNA literally crosses from one homologous chromosome to another.

20) If you were looking at a set of human chromosomes under the microscope, you would know when you saw the X chromosome in part because it is A) larger than the Y chromosome. B) smaller than the Y chromosome. C) the same size as the Y chromosome. D) genetically identical to the Y chromosome. E) larger and genetically identical to the Y chromosome.

A) larger than the Y chromosome. Explanation: Y chromosomes are much smaller than X chromosomes, but they do share a small region of homology.

52) What creates genetically different offspring in both asexual and sexual reproduction? A) mutations B) mitosis C) meiosis D) mutations and mitosis E) mitosis and meiosis

A) mutations Explanation: Mutation changes DNA sequences and thus the genetic information in organisms which inherit the mutated DNA.

57) In the presence of parasites, a hermaphroditic roundworm will reproduce A) sexually, producing varied offspring B) sexually, producing identical offspring C) asexually, producing identical offspring D) asexually, producing varied offspring E) None of the above are correct.

A) sexually, producing varied offspring Explanation: A hermaphrodite worm can reproduce sexually, producing varied offspring. It can also self-reproduce, in which case the offspring are identical to the parent. With a parasite threat, sexual reproduction will yield variable offspring and a higher probability that some of those offspring will survive.

49) Fraternal twins (dizygotic) result from the fertilization of A) two eggs and two sperm. B) two eggs and one sperm. C) one egg and two sperm. D) one egg and one sperm. E) two eggs and one sperm OR one egg and two sperm.

A) two eggs and two sperm. Explanation: Fraternal twins are the result of two fertilization events.

38) If a haploid cell goes through mitosis it will generate A) two haploid cells. B) two diploid cells. C) four haploid cells. D) four diploid cells. E) No answer is correct.

A) two haploid cells. Explanation: Mitosis produces cells with identical genetic contents to the starting cells.

56) Researchers exposed the microscopic roundworm, Caenorhabditis elegans, to disease causing bacteria. The roundworm can reproduce either asexually or sexually. In the presence of live bacteria, more roundworms reproduced sexually, and the resulting offspring were A) unique, giving the roundworms a better chance of survival. B) identical, giving the roundworms a better chance for survival. C) identical, giving the bacteria a greater chance to kill the entire round worm population. D) unique, giving the roundworms a more energy-conserving type of reproduction. E) All of the answer choices are correct.

A) unique, giving the roundworms a better chance of survival. Explanation: The roundworm, C. elegans is able to change from asexual to sexual reproduction. Switching to sexual reproduction occurs when the worms are challenged by a stressor, such as parasitic bacteria. Sexual reproduction increases genetic variation with more offspring surviving.

10) After the completion of meiosis in human males, a diploid germ cell has produced cells with half the original chromosome number, generating ________ haploid cells. A) 2 B) 3 C) 4 D) 23 E) 46

C) 4 Explanation: Since meiosis starts with a diploid cell that has replicated its DNA to yield four sets of chromosomes, four haploid cells would have to be the result.

39) Genes A and B are on the same chromosome. What gametes could an individual with the allele combination AABB produce? A) AABB B) A C) AB D) B E) AAB

C) AB Explanation: Each gamete gets one allele per gene.

18) The chromosomal designation for a human male is A) XX. B) XO. C) XY. D) YY. E) XXX.

C) XY. Explanation: Male mammals such as human males have two different sex chromosomes.

24) If you were told that you would get extra credit for finding a model showing chromsomes separating while sister chromatids were still attached, you would look for a model of A) prophase I. B) prophase II. C) anaphase I. D) metaphase I. E) anaphase II.

C) anaphase I. Explanation: At the end of anaphase I, chromosomes separate to opposite poles, but meiosis II still needs to occur.

17) The human chromosomes that do not determine an individual's sex are A) not found in pairs. B) the "X" and "Y" chromosomes. C) autosomes. D) sex chromosomes. E) No answer is correct.

C) autosomes. Explanation: Autosomes are the majority of the DNA in a eukaryotic nucleus, but they do not determine sex in organisms with distinct sex chromosomes.

41) Which of the following will occur in meiosis but not in mitosis? A) metaphase B) cytokinesis C) crossing over D) DNA replication E) chromosome condensation

C) crossing over Explanation: Mitosis lacks any exchange of DNA between homologs.

1) Chromosomes that look alike and carry the same genes are A) the X and Y chromosome. B) heterologous chromosomes. C) homologous chromosomes. D) found in females only. E) found in males only.

C) homologous chromosomes. Explanation: Homologous chromosomes are the corresponding chromosomes in a genome which came from the two parental organisms.

29) A cell having one or more complete sets of extra chromosomes A) cannot be produced by meiosis. B) cannot participate in fertilization. C) is polyploid. D) is haploid. E) is dizygotic.

C) is polyploid. Explanation: Cells with extra sets of chromosomes are polyploid; an example would be a diploid gamete.

13) Sexual reproduction includes A) mitosis, fission, and fertilization. B) mitosis, meiosis, and budding. C) meiosis, fertilization, and mitosis. D) meiosis, fertilization, and transduction. E) fertilization, fission, and meiosis.

C) meiosis, fertilization, and mitosis. Explanation: Meiosis produces gametes, which can then undergo fertilization..

9) A diploid germ cell will produce cells with half the number of chromosomes, haploid cells, in A) fertilization. B) mitosis. C) meiosis. D) replication. E) mutation.

C) meiosis. Explanation: Meiosis reduces the number of copies of each chromosome from 2 to 1.

23) In meiosis, homologous chromosomes align next to one another during A) interphase I. B) metaphase II. C) prophase I. D) metaphase I. E) prophase II.

C) prophase I. Explanation: Homologous chromosomes align during prophase I and crossing over can occur.

34) Why is it essential that meiosis produce haploid cells? A) so that the number of chromosomes will double each generation B) to produce haploid offspring C) to prevent the number of chromosomes from doubling each generation D) to produce diploid gametes E) to allow asexual reproduction

C) to prevent the number of chromosomes from doubling each generation Explanation: Fusion of haploid gametes restores the normal diploid state when a zygote forms.

5) Diploid means having A) one homologous set of chromosomes. B) three homologous sets of chromosomes. C) two homologous sets of chromosomes. D) two chromosomes in each somatic cell. E) two chromosomes in each gamete.

C) two homologous sets of chromosomes. Explanation: Diploid cells have two copies of every chromosome.

25) Sexual reproduction and meiosis generate genetic variability by A) random fertilization. B) crossing over. C) random alignment. D) All answers are correct.

D) All answers are correct. Explanation: Meiosis generates genetic variability by several means. This variability may benefit a species, since the variable progeny will potentially respond differently under different conditions.

19) The chromosomal designation for a human female is A) XYY. B) XY. C) YY. D) XX. E) No answer is correct.

D) XX. Explanation: Human females, like other female mammals, have two X chromosomes.

12) A zygote is A) a haploid cell. B) a gamete. C) a direct product of meiosis. D) a diploid cell. E) All answers are correct.

D) a diploid cell. Explanation: A zygote, which all of us were at one time, is the first diploid cell in the life of an organism.

35) When a diploid germ cell in a male goes through meiosis, it will generate A) two haploid cells. B) four diploid cells. C) two diploid cells. D) four haploid cells. E) This is not possible.

D) four haploid cells. Explanation: Meiosis starts with a diploid cell. In males, four haploid cells are produced at the end of meiosis.

22) In meiosis, DNA replicates during A) prophase I. B) prophase II. C) interphase prior to meiosis II. D) interphase prior to meiosis I. E) both prophase I and prophase II.

D) interphase prior to meiosis I. Explanation: Meiosis, by having one replication but two divisions, produces to haploid cells.

21) The Y chromosome A) is larger than the X chromosome. B) contains more genes than the X chromosome. C) is the same size as the X chromosome. D) is smaller than the X chromosome. E) is genetically identical to the X chromosome.

D) is smaller than the X chromosome. Explanation: The X chromosome is much larger than the Y.

51) What two processes result in genetically different products? A) mitosis and meiosis B) mitosis and asexual reproduction C) meiosis and asexual reproduction D) meiosis and sexual reproduction E) mitosis and sexual reproduction

D) meiosis and sexual reproduction Explanation: Mitosis is designed to produce genetically identical cells, while meiosis and sexual reproduction lead to new genetic combinations.

14) Mitotic cell division creates identical copies by replicating a cell's DNA ________ and then dividing ________. A) once; twice B) twice; once C) twice; twice D) once; once E) No answer is correct.

D) once; once Explanation: Mitosis in eukaryotes serves to make organisms larger and to repair tissue, and for replication in some cases.

28) What process leads to siblings only sharing, on average, 25% of their genetic material? A) asexual reproduction B) semiconservative replication C) random fertilization D) random orientation E) mutation

D) random orientation Explanation: In meiosis I, the alignment of chromosomes during metaphase is a random process, such that resulting gametes will contain different mixes of paternal and maternal chromosomes.

42) If a chromosome in one of your bone cells becomes mutated, you will not pass this mutation onto your children because A) somatic cells cannot undergo mitosis. B) germ cells cannot undergo meiosis. C) germ cells cannot undergo mitosis. D) somatic cells cannot undergo meiosis.

D) somatic cells cannot undergo meiosis. Explanation: Somatic cells, distinct from germ cells, do not produce gametes for starting a new generation.

6) If human gametes were diploid A) the products of fertilization would have the same number of chromosomes as their parents. B) the products of fertilization would have fewer chromosomes than their parents. C) fertilization could not occur. D) the products of fertilization would have more chromosomes than their parents. E) the embryo would be diploid.

D) the products of fertilization would have more chromosomes than their parents. Explanation: A doubling of chromosomes in every generation would lead to a genetic disaster for diploid organisms.