LSN 13: Meiosis

Clone

(1) A group of genetically identical individuals or cells. (2) In popular usage, an individual that is genetically identical to another individual. (3) As a verb, to make one or more genetic replicas of an individual or cell. See also gene cloning.

Fertilization

(1) The union of haploid gametes to produce a diploid zygote. (2) The addition of mineral nutrients to the soil.

Haploid cell

A cell containing only one set of chromosomes (n).

Diploid cell

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

Recombinant chromosomes

A chromosome created when crossing over combines DNA from two parents into a single chromosome.

Sex chromosomes

A chromosome responsible for determining the sex of an individual.

Autosomes

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Alternation of generations

A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae.

Meiosis

A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell. Meiosis I: The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell. Meiosis II: The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Homologs

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother. Also called a homologous pair.

Locus

A specific place along the length of a chromosome where a given gene is located.

27) Which of the following events happens at the conclusion of meiosis I? A) Homologous chromosomes of a pair are separated from each other. B) The chromosome number per cell remains the same. C) Sister chromatids are separated. D) Four daughter cells are formed.

A) Homologous chromosomes of a pair are separated from each other.

33) Which diagram represents anaphase I of meiosis? A) I B) II C) IV D) V

A) I

35) Which sample of DNA might be from a cell that stopped the process of cell division in G0 phase of the cell cycle prior to meiosis? A) I B) II C) III D) either I or II

A) I

37) Which sample of DNA might represent a zygote? A) I B) II C) III D) either I or II

A) I

15) Which of the life cycles is typical for animals? A) I only B) II only C) III only D) I and III

A) I only

23) If a cell has completed meiosis I and the first cytokinesis, and is just beginning meiosis II, which of the following is an appropriate description of its genetic contents? A) It has half the amount of DNA as the cell that began meiosis. B) It has half the chromosomes but twice the DNA of the parent cell. C) It has one-fourth the DNA and one-half the chromosomes as the parent cell. D) It is genetically identical to another cell formed from the same meiosis I event.

A) It has half the amount of DNA as the cell that began meiosis.

54) How does natural selection apply to sexual reproduction as opposed to asexual reproduction? A) Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction. B) Sexual reproduction results in the greatest number of new mutations. C) Sexual reproduction allows the greatest number of offspring to be produced. D) Sexual reproduction utilizes far less energy than asexual reproduction.

A) Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction.

45) Which of the following statements describes a major difference between mitosis and meiosis I in a diploid organism? A) Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I. B) Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis II. C) DNA replication takes place prior to mitosis, but not before meiosis I. D) Only meiosis I results in daughter cells that contain identical genetic information.

A) Sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I.

57) Imagine that there are 25 different species of protists living in a tide pool. Some of these species reproduce both sexually and asexually, and some of them can reproduce only asexually. The pool gradually becomes infested with disease-causing viruses and bacteria. Which species are more likely to thrive in the changing environment? A) The sexually reproducing species is likely to thrive. B) The asexually reproducing species is likely to thrive. C) Sexually and asexually reproducing species are equally likely to thrive. D) Neither species will be able to thrive.

A) The sexually reproducing species is likely to thrive.

18) In a life cycle such as that shown in part III of the figure above, if the zygote's chromosome number is ten, which of the following statements will be true? A) The sporophyte's chromosome number per cell is ten and the gametophyte's is five. B) The sporophyte's chromosome number per cell is five and the gametophyte's is ten. C) The sporophyte and gametophyte each have ten chromosomes per cell. D) The sporophyte and gametophyte each have five chromosomes per cell.

A) The sporophyte's chromosome number per cell is ten and the gametophyte's is five.

1) A human cell containing 22 autosomes and a Y chromosome is A) a sperm. B) an egg. C) a zygote. D) a somatic cell of a male.

A) a sperm.

13) Which of the following processes might produce a human zygote with 45 chromosomes? A) an error in meiotic anaphase occurring in either an egg or sperm B) failure of the egg nucleus to be fertilized by the sperm C) failure of an egg to complete meiosis II D) incomplete cytokinesis during spermatogenesis after meiosis I

A) an error in meiotic anaphase occurring in either an egg or sperm

50) During which of the following processes does independent assortment of chromosomes occur? A) in meiosis I only B) in meiosis II only C) in mitosis and meiosis I D) in mitosis and meiosis II

A) in meiosis I only

3) Meiosis II is similar to mitosis in that A) sister chromatids separate during anaphase. B) DNA replicates before the division. C) the daughter cells are diploid. D) homologous chromosomes synapse.

A) sister chromatids separate during anaphase.

52) Independent assortment of chromosomes is a result of which of the following processes? A) the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I B) the random combinations of eggs and sperm during fertilization C) the random distribution of the sister chromatids to the two daughter cells during anaphase II D) the diverse combination of alleles that may be found within any given chromosome

A) the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

12) A triploid cell contains three sets of homologous chromosomes. If a cell of a diploid species that normally has 42 chromosomes per cell is triploid, this cell would be expected to have which of the following sets of chromosomes? A) 63 chromosomes in 31 1/2 pairs B) 63 chromosomes in 21 sets of 3 C) 63 chromosomes, each with 3 sister chromatids D) 21 chromosome pairs and 21 unique chromosomes

B) 63 chromosomes in 21 sets of 3

10) Which of the following statements describes an example of alternation of generations? A) A grandparent and grandchild each have dark hair, but the parent has blond hair. B) A diploid plant (sporophyte) produces a spore by meiosis that gives rise to a multicellular, haploid pollen grain (gametophyte). C) A diploid animal produces gametes by meiosis, and the gametes undergo fertilization to produce a diploid zygote. D) A haploid mushroom produces gametes by mitosis, and the gametes undergo fertilization, which is immediately followed by meiosis.

B) A diploid plant (sporophyte) produces a spore by meiosis that gives rise to a multicellular, haploid pollen grain (gametophyte).

47) Which of the following statements describes one characteristic of each chromosome in a cell during the entire process of meiosis I? A) Each chromosome is paired with a homologous chromosome. B) Each chromosome consists of two sister chromatids joined by a centromere. C) Each chromosome consists of a single strand of DNA. D) Each chromosome is joined with its homologous pair to form a synaptonemal complex.

B) Each chromosome consists of two sister chromatids joined by a centromere.

36) Which sample of DNA might represent an animal cell in the G2 phase of the cell cycle prior to meiosis? A) I B) II C) III D) both I and II

B) II

I. Prophase I II. Metaphase I III. Anaphase I IV. Telophase I V. Prophase II VI. Metaphase II VII.Anaphase II VIII. Telophase II 31) Homologous chromosomes are aligned at the equator of the spindle. A) I B) II C) IV D) VI

B) II

17) Which of the life cycles is typical for most fungi and some protists? A) I only B) II only C) III only D) I and II

B) II only

8) Eukaryotic sexual life cycles show tremendous variation. Which of the following characteristics do all sexual life cycles have in common? I. Alternation of generations II. Meiosis III. Fertilization IV. Gametes V. Spores A) I, II, and IV B) II, III, and IV C) II, IV, and V D) I, II, III, IV, and V

B) II, III, and IV

5) Which of the following statements is correct in comparing sexual and asexual reproduction? A) Asexual reproduction, but not sexual reproduction, is characteristic of only plants and fungi. B) In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring. C) In asexual reproduction, offspring are produced by fertilization without meiosis. D) Asexual reproduction produces only haploid offspring.

B) In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring

22) Which of the following statements correctly describes a karyotype? A) It is a display of all of the cell types in an organism. B) It is an organized image of a cell's chromosomes. C) It reveals the appearance of an organism. D) It is a display of a cell's mitotic stages.

B) It is an organized image of a cell's chromosomes.

19) Which of the following characteristics do homologous chromosomes exhibit? A) They carry information for different traits. B) They carry information for the same traits. C) They carry the same alleles. D) They align on the metaphase plate in meiosis II.

B) They carry information for the same traits.

9) Which of the following processes occurs in a plant's sexual life cycle? A) sporophytes produce gametes by meiosis B) gametophytes produce gametes by mitosis C) gametophytes produce gametes by meiosis D) sporophytes produce gametes by mitosis

B) gametophytes produce gametes by mitosis

46) Crossing over of chromosomes normally takes place during which of the following processes? A) meiosis II B) meiosis I C) mitosis D) mitosis and meiosis II

B) meiosis I

2) The two homologs of a pair move toward opposite poles of dividing cell during A) mitosis. B) meiosis I. C) meiosis II. D) fertilization.

B) meiosis I.

6) At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype? A) prophase B) metaphase C) anaphase D) interphase

B) metaphase

48) During which of the following processes do homologous pairs of chromosomes align adjacent to one another at the metaphase plate of a cell? A) metaphase of mitosis B) metaphase I of meiosis C) telophase II of meiosis D) metaphase II of meiosis

B) metaphase I of meiosis

3) Asexual reproduction occurs during which of the following processes? A) meiosis B) mitosis C) fertilization D) the exchange of chromosomes between organisms of different species

B) mitosis

29) Which of the following processes occurs in meiosis but not in mitosis? A) chromosome replication B) synapsis of chromosomes C) alignment of chromosomes at the equator D) condensation of chromosomes

B) synapsis of chromosomes

41) Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm? A) four B) two C) eight D) a diploid number

B) two

1) If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants? A) Backtrack through her previous experiments to obtain another plant with the same traits. B) Breed this plant with another plant with much weaker traits. C) Clone the plant. D) Force the plant to self-pollinate to obtain an identical one.

C) Clone the plant.

53) Which of the following processes occurs when homologous chromosomes cross over in meiosis I? A) Two sister chromatids get tangled, resulting in one re-sequencing its DNA. B) Two sister chromatids exchange identical pieces of DNA. C) Corresponding segments of non-sister chromatids are exchanged. D) Maternal alleles are "corrected" to be like paternal alleles and vice versa.

C) Corresponding segments of non-sister chromatids are exchanged.

42) Which of the following processes occur during meiosis but not mitosis? A) Haploid cells fuse to form diploid cells. B) Haploid cells multiply into more haploid cells. C) Diploid cells form haploid cells. D) A diploid cell combines with a haploid cell.

C) Diploid cells form haploid cells.

7) Which of the following statements is true of a species that has a chromosome number of 2n = 16? A) The species is diploid with 32 chromosomes per cell. B) The species has 16 sets of chromosomes per cell. C) Each diploid cell has eight homologous pairs of chromosomes. D) A gamete from this species has four chromosomes.

C) Each diploid cell has eight homologous pairs of chromosomes.

24) The somatic cells of a privet shrub each contain a total of 46 chromosomes. How do the chromosomes of this plant differ from the chromosomes of humans, who also have a total of 46? A) Privet shrub cells cannot reproduce sexually. B) Privet shrub sex cells have chromosomes that can synapse with human chromosomes in the laboratory. C) Genes of privet shrub chromosomes are significantly different than those in humans. D) Privet shrubs must be metabolically more like animals than like other shrubs.

C) Genes of privet shrub chromosomes are significantly different than those in humans.

16) Which of the life cycles is typical for plants and some algae? A) I only B) II only C) III only D) I and III

C) III only

58) In eukaryotes, genetic information is passed to the next generation by processes that include mitosis or meiosis. Which of the following explanations correctly identifies the process and supports the claim that heritable information is passed from one generation to another? A) During mitosis, DNA replication occurs twice within the cell cycle to insure a full set of chromosomes within each of the daughter cells produced. B) Mitosis, followed by cytokinesis, produces daughter cells that are genetically different from the parent cell, thus insuring variation within the population. C) In asexual reproduction, a single individual is the sole parent and passes copies of its genes to its offspring without the fusion of gametes. D) Single-celled organisms can fuse their cells, reproducing asexually through mitosis to form new cells that are not identical to the parent cell.

C) In asexual reproduction, a single individual is the sole parent and passes copies of its genes to its offspring without the fusion of gametes.

21) Which of the following statements is correct regarding the human X chromosomes? A) It is present in every somatic cell of males and females. B) It is the same size as other chromosomes and has the same number of genes. C) It carries genes that determine an individual's biological sex. D) It is referred to as an autosome.

C) It carries genes that determine an individual's biological sex.

44) Which of the following statements describes a major difference between meiosis II and mitosis in a diploid animal? A) Homologous chromosomes align on the metaphase plate in meiosis II. B) Sister chromatids separate in mitosis, and homologous chromosomes separate in meiosis II. C) Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells. D) Crossing over of chromosomes takes place in meiosis II.

C) Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells.

26) How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I? A) The cells have half the number of chromosomes and half the amount of DNA. B) The cells have the same number of chromosomes and half the amount of DNA. C) The cells have half the number of chromosomes and one-fourth the amount of DNA. D) The cells have half the amount of cytoplasm and twice the amount of DNA.

C) The cells have half the number of chromosomes and one-fourth the amount of DNA.

49) During which of the following phases of meiosis do centromeres split and sister chromatids migrate to opposite poles of the cell? A) anaphase I B) telophase I C) anaphase II D) telophase II

C) anaphase II

55) The bulldog ant has a diploid number of two chromosomes. Therefore, following meiosis, each daughter cell will have a single chromosome. In addition to mutations, how might genetic diversity be generated in this species? A) crossing over only B) independent assortment only C) crossing over and random fertilization D) nothing else

C) crossing over and random fertilization

14) In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common? A) length and position of the centromere only B) length, centromere position, and staining pattern only C) length, centromere position, staining pattern, and traits coded for by their genes D) They have nothing in common except that they are X-shaped.

C) length, centromere position, staining pattern, and traits coded for by their genes

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure. 39) If a female of this species has one chromosome 12 with a blue gene and another chromosome 12 with an orange gene, and has both number 19 chromosomes with short genes, which of the following combinations of genes will her eggs have? A) only blue short gene eggs B) only orange short gene eggs C) one half blue short and one half orange short gene eggs D) three fourths blue short and one fourth orange short gene eggs

C) one half blue short and one half orange short gene eggs

30) When chiasmata can first be seen in cells using a microscope, which of the following processes has most likely occurred? A) meiosis II B) anaphase II C) prophase I D) the separation of homologs

C) prophase I

56) Which of the following processes facilitates the fastest way for organisms to adapt to a changing environment? A) mutation B) asexual reproduction C) sexual reproduction D) mitosis

C) sexual reproduction

5) If we continue to follow the cell lineage from question 4, then the DNA content of a single cell at metaphase of meiosis II will be A) 0.25x. B) 0.5x. C) x. D) 2x.

C) x.

4) If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I will be A) 0.25x. B) 0.5x. C) x. D) 2x.

D) 2x.

4) Quaking aspen trees can send out underground stems for asexual reproduction. Sexual reproduction is not as common, but when it does happen, the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems? A) 9 B) 10 C) 19 D) 38

D) 38

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure. 40) A female with a paternal set of one orange and one long gene chromosome and a maternal set comprised of one blue and one short gene chromosome would be expected to produce which of the following types of eggs after meiosis? A) All eggs will have maternal types of gene combinations. B) All eggs will have paternal types of gene combinations. C) Half the eggs will have maternal and half will have paternal combinations. D) Each egg has a one-fourth chance of having either blue long, blue short, orange long, or orange short combinations.

D) Each egg has a one-fourth chance of having either blue long, blue short, orange long, or orange short combinations.

11) A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism? A) It must be human. B) It must be an animal. C) It reproduces sexually. D) It produces gametes with 23 chromosomes.

D) It produces gametes with 23 chromosomes.

59) Genetic variation leads to genetic diversity in populations and is the raw material for evolution. Biological systems have multiple processes, such as reproduction, that affect genetic variation. They are evolutionarily conserved and shared by various organisms. Which of the following statements best represents the connection between reproduction and evolution? A) Plants that use sexual reproduction are rare since this type of reproduction in plants does not contribute to genetic diversity. B) In order to increase genetic diversity for evolution in sexually reproducing organisms, mutations must occur in the zygote after fertilization. C) Since prokaryotic organisms reproduce asexually, there is no mechanism for them to add genetic diversity for evolution. D) Sexual reproduction increases genetic variation because random mutations can be shuffled between organisms.

D) Sexual reproduction increases genetic variation because random mutations can be shuffled between organisms.

25) Which of the following statements describes the chromosomal makeup of each daughter cell after telophase of meiosis I? A) The cells are diploid, and the chromosomes are each composed of a single chromatid. B) The cells are diploid, and the chromosomes are each composed of two chromatids. C) The cells are haploid, and the chromosomes are each composed of a single chromatid. D) The cells are haploid, and the chromosomes are each composed of two chromatids.

D) The cells are haploid, and the chromosomes are each composed of two chromatids.

34) Which diagram represents anaphase II of meiosis? A) I B) III C) IV D) V

D) V

I. Prophase I II. Metaphase I III. Anaphase I IV. Telophase I V. Prophase II VI. Metaphase II VII.Anaphase II VIII. Telophase II 32) Centromeres of sister chromatids disjoin and chromatids separate. A) III B) IV C) V D) VII

D) VII

51) For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes based on the independent assortment of chromosomes during meiosis? A) 23 B) 46 C) about 1,000 D) about 8 million

D) about 8 million

43) During which of the following phases of meiosis do homologous chromosomes separate? A) anaphase II B) prophase I C) mitosis D) anaphase I

D) anaphase I

20) Many organisms spend most of their life cycle in the diploid state. If meiosis produces haploid cells, how is the diploid number restored for these types of organisms? A) by DNA replication B) through the transcription of DNA to RNA C) by synapsis of the homologous pairs of chromosomes during prophase of meiosis I D) by fertilization

D) by fertilization

28) During which of the following processes do sister chromatids separate from each other? A) during meiosis I only B) during meiosis II only C) during both mitosis and meiosis I D) during both mitosis and meiosis II

D) during both mitosis and meiosis II

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure. 38) A certain female's number 12 chromosomes both have the blue gene and number 19 chromosomes both have the long gene. As cells in her ovaries undergo meiosis, which of the following combinations of genes and chromosomes will her eggs have? A) either two number 12 chromosomes with blue genes or two with orange genes B) either two number 19 chromosomes with long genes or two with short genes C) either one blue or one orange gene in addition to either one long or one short gene D) one chromosome 12 with one blue gene and one chromosome 19 with one long gene

D) one chromosome 12 with one blue gene and one chromosome 19 with one long gene

2) Which of the following statements defines a genome? A) the complete set of an organism's polypeptides B) the complete set of a species' polypeptides C) a karyotype D) the complete set of an organism's genes and other DNA sequences

D) the complete set of an organism's genes and other DNA sequences

4. Describe three main sources of genetic variability: independent assortment, crossing over, and random fertilization.

Independent assortment: Mendel's second law, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes. Crossing over: The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis. Crossing over produces recombinant chromosomes, individual chromosomes that carry genes (DNA) from two different parets. Random fertilization: each male and female gamete represent one of millions of possible chromosome combinations due to independent assortment. The fusion of a male and female gamete during fertilization will produce a zygote with one of trillions of possible diploid combinations.

3. Outline the key events that occur during each phase of meiosis I and meiosis II, and be able to compare and contrast mitosis and meiosis.

Meiosis I: 1. Synapsis and crossing over. During prophase I, duplicated homologs pair up and crossing over occurs. Synapsis and crossing over do not occur during prophase of mitosis. 2. Alignment of homologous pairs at the metaphase plate. At metaphase I of meiosis, pairs of homologs are positioned at the metaphase plate, rather than individual chromosomes, as in metaphase of mitosis. 3. Separation of homologs. At anaphase I of meiosis, the duplicated chromosomes of each homologous pair move toward opposite poles, but the sister chromatids of each duplicated chromosome remain attached. In anaphase of mitosis, by contrast, sister chromatids separate.

Sexual reproduction

Reproduction arising from fusion of two gametes.

Chiasmata

The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase I between homologous nonsister chromatids. Chiasmata become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion.

Zygote

The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg.

Asexual reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes. In most cases, the offspring are genetically identical to the parent.

Life cycle

The generation-to-generation sequence of stages in the reproductive history of an organism.

Synapsis

The pairing and physical connection of one duplicated chromosome to its homolog during prophase I of meiosis.

Crossing over

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Genetics

The scientific study of heredity and hereditary variation.

Heredity

The transmission of traits from one generation to the next.