Chapter 13: Meiosis And Sexual Life Cycles

Front 1

allele

Back 1

Any of the alternative versions of a gene that produce distinguishable phenotypic effects.

Front 2

alternation of generations

Back 2

A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte

Front 3

asexual reproduction

Back 3

The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical to the parent.

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autosome

Back 4

A chromosome that is not directly involved in determining sex

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chiasma

Back 5

The X-shaped, microscopically visible region where homologous nonsister chromatids have exchanged genetic material through crossing over during meiosis, the two homologs remaining associated due to sister chromatid cohesion.

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clone

Back 6

(1) A lineage of genetically identical individuals or cells. (2) In popular usage, a single individual organism 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.

Front 7

crossing over

Back 7

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

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diploid cell

Back 8

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

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gametophyte

Back 9

In organisms (plants and some algae) that have alternation of generations, the multicellular haploid form that produces haploid gametes by mitosis. The haploid gametes unite and develop into sporophytes.

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gene

Back 10

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

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genetics

Back 11

The scientific study of heredity and hereditary variation.

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haploid cell

Back 12

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

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heredity

Back 13

The transmission of traits from one generation to the next.

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homologous chromosomes

Back 14

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 homologs, or a homologous pair.

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karyotype

Back 15

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

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life cycle

Back 16

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

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locus

Back 17

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

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meiosis

Back 18

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.

Front 19

meiosis I

Back 19

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.

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meiosis II

Back 20

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.

Front 21

recombinant chromosome

Back 21

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

Front 22

sex chromosome

Back 22

A chromosome responsible for determining the sex of an individual.

Front 23

sexual reproduction

Back 23

A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the parents.

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somatic cell

Back 24

Any cell in a multicellular organism except a sperm or egg

Front 25

spore

Back 25

(1) In the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis. A spore can divide by mitosis to develop into a multicellular haploid individual, the gametophyte, without fusing with another cell. (2) In fungi, a haploid cell, produced either sexually or asexually, that produces a mycelium after germination.

Front 26

sporophyte

Back 26

In organisms (plants and some algae) that have alternation of generations, the multicellular diploid form that results from the union of gametes. The sporophyte produces haploid spores by meiosis that develop into gametophytes.

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synapsis

Back 27

The pairing and physical connection of replicated homologous chromosomes during prophase I of meiosis.

Front 28

variation

Back 28

Differences between members of the same species.

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zygote

Back 29

The diploid product of the union of haploid gametes during fertilization

Front 30

How many genes are present in the human genome? ( Concept 13.1)

Back 30

Your Answer: a virtually infinite number
Correct Answer:tens of thousands

No. Although the precise number of genes in the genome is not yet known, it has been estimated by many scientists, and is certainly finite.

Front 31

What is a locus? ( Concept 13.1)

Back 31

Your Answer:the precise location of a gene on a chromosome
Correct. The location of a gene within the genome, including the identity of the particular chromosome that it maps to and its specific position on that chromosome, is called its locus.

Front 32

Sexual and asexual reproduction are alike in that _____. ( Concept 13.1)

Back 32

Your Answer:they both require meiosis to complete the reproductive cycle
Correct Answer:they can both occur in multicellular organisms

No. Sexual reproduction depends on meiosis, but asexual reproduction only involves mitosis.

Front 33

A clone is the product of _____. ( Concept 13.1)

Back 33

Your Answer:The first and third answers are correct.
Correct. In asexual reproduction, an organism produces genetically identical progeny, or clones, by mitosis.

Front 34

Unless the chromosomes were stained to show band patterns, a karyotype would be least likely to show which of the following? ( Concept 13.2)

Back 34

Your Answer:part of a chromosome turned around
Correct. An inversion, which affects neither the number of chromosomes nor the length of a chromosome, is generally difficult to detect without staining to show chromosomal bands

Front 35

A karyotype is _____. ( Concept 13.2)

Back 35

Your Answer:a photograph of all of an individual's chromosomes
Correct. Karyotypes, ordered displays of an individual's chromosomes, are useful in identifying chromosomal abnormalities.

Front 36

Fertilization produces ___________. ( Concept 13.2)

Back 36

Your Answer:a diploid zygote
Correct. Fertilization always involves the fusion of gametes and produces a diploid zygote.

Front 37

Which one, if any, of the following statements is true? ( Concept 13.2)

Back 37

Your Answer:Diploid cells can divide by meiosis.
Correct Answer:all of the above

No. Diploid cells can undergo meiosis, but there is a better answer.

Front 38

Which of the following is part of the life cycle called alternation of generations? ( Concept 13.2)

Back 38

Your Answer:all of the above
Correct. In alternation of generations, zygotes give rise to multicellular, diploid sporophytes, and spores give rise to multicellular, haploid gametophytes.

Front 39

The sexual cycle of the multicellular algal genus Fucus involves _____. ( Concept 13.2)

Back 39

Your Answer:both mitosis and meiosis but not fertilization
Correct Answer:mitosis, meiosis, and fertilization

No. This answer is correct, but there is a better response.

Front 40

A life cycle in which the only multicellular form is haploid is most typical of _____. ( Concept 13.2)

Back 40

Your Answer:fungi
Correct. In most fungi, the multicellular form is haploid, and fertilization (and creation of a zygote) is immediately followed by meiosis.

Front 41

Which of the following results in cells that contain half the parental chromosome number? ( Concept 13.2)

Back 41

Your Answer:meiosis
Correct. The two cell divisions of meiosis, I and II, produce four haploid daughter cells.

Front 42

In sexually reproducing species, the chromosome number remains stable over time because _____ and _____ always alternate. ( Concept 13.2)

Back 42

Your Answer:meiosis; mitosis
Correct Answer:meiosis; fertilization

No. Meiosis reduces the number of chromosomes, but mitosis has no effect on chromosome number.

Front 43

The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit? ( Concept 13.2)

Back 43

Your Answer:44
Correct. Haploid sex cells contain half as many chromosomes as diploid somatic cells.

Front 44

In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing _____ chromosomes. ( Concept 13.2)

Back 44

Your Answer:5
Correct. Haploid sex cells contain half as many chromosomes as diploid somatic cells.

Front 45

How many pairs of autosomes do humans have? ( Concept 13.2)

Back 45

Your Answer:22
Correct. Humans have 22 pairs of autosomes and one pair of sex chromosomes.

Front 46

Sister chromatids ___________. ( Concept 13.2)

Back 46

Your Answer:are identical copies of each other formed during DNA synthesis
Correct. Sister chromatids are identical and participate in both mitosis and meiosis.

Front 47

Which of the following statements about homologous chromosomes is correct? ( Concept 13.2)

Back 47

Correct. The chromosomes that make up a pair are called homologous chromosomes, and they carry genes controlling the same inherited characters.

Front 48

Humans have 46 chromosomes. This number of chromosomes will be found in _____. ( Concept 13.2)

Back 48

Your Answer:all the cells of the body
Correct Answer:liver cells

No. This is not true for gametes.

Front 49

When we say that an organism is haploid, we mean that _____. ( Concept 13.2)
Your Answer:its cells have half of one set of chromosomes

Back 49

Correct Answer:its cells have a single set of chromosomes

No. It has one entire set.

Front 50

Which one of the following is a function of mitosis in humans? ( Concept 13.2)

Back 50

Your Answer:multiplication of body cells
Correct. This is a function of mitosis in humans. It is mitosis that enables a multicellular adult to form from a fertilized egg and produces cells for growth and tissue repair.

Front 51

Somatic cells in humans contain _____ set(s) of chromosomes and are therefore termed _____. ( Concept 13.2)

Back 51

Your Answer:two; haploid
Correct Answer:two; diploid

No. This answer is partially correct.

Front 52

Nearly all life cycles have both haploid and diploid phases. Usually, the transition from haploid to diploid takes place _____. ( Concept 13.2)

Back 52

Your Answer:at fertilization, when gametes fuse
Correct. The union of haploid gametes at fertilization produces the zygote, or fertilized egg, which marks the beginning of the diploid phase of the life cycle.

Front 53

Spores and gametes are different in that _____. ( Concept 13.2)

Back 53

Your Answer:only the formation of gametes contributes to genetic variation
Correct Answer:gametes can fuse to form a zygote, but spores can develop into independent organisms without first forming a zygote

No. Each cycle of chromosome halving and doubling contributes to genetic variation among offspring.

Front 54

At the end of telophase I of meiosis and the first cytokinesis, there are _____. ( Concept 13.3)

Back 54

Your Answer:two diploid cells
Correct Answer:two haploid cells

No. Two diploid cells are the result of the completion of the mitotic cell cycle.

Front 55

What is the result when a diploid cell undergoes meiosis? ( Concept 13.3)

Back 55

Your Answer:four haploid cells
Correct. The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.

Front 56

Synapsis occurs during _____. ( Concept 13.3)

Back 56

Your Answer:prophase I
Correct. Synapsis is the pairing of homologous chromosomes during prophase I.

Front 57

Which of the following occurs during anaphase II? ( Concept 13.3)

Back 57

Your Answer:Sister chromatids separate and migrate toward opposite poles.
Correct. This occurs during anaphase II.

Front 58

Which of the following occurs during anaphase I? ( Concept 13.3)

Back 58

Your Answer:Sister chromatids separate and migrate toward opposite poles.
Correct Answer:Homologs separate and migrate toward opposite poles.

No. This occurs during anaphase II.

Front 59

Cytokinesis is the _____. ( Concept 13.3)

Back 59

Your Answer:division of one cell into two
Correct. Cytokinesis normally accompanies both telophase I and telophase II, as well as the telophase of mitosis.

Front 60

What is the function of meiosis? ( Concept 13.3)

Back 60

Your Answer:to make cells with a haploid (half that of the parents) number of chromosomes
Correct. The two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.

Front 61

Crossing over occurs during _____. ( Concept 13.3)

Back 61

Your Answer:prophase I
Correct. Crossing over resulting in genetic recombination occurs during this phase.

Front 62

Regions of chromosomes where nonsister chromatids cross over are called _____. ( Concept 13.3)

Back 62

Your Answer:chiasmata
Correct. Chiasmata are regions where crossing over has occurred.

Front 63

The synaptonemal complex _____. ( Concept 13.3)

Back 63

Your Answer:physically connects homologous chromosomes during prophase I
Correct. The synaptonemal complex helps to line homologous chromosomes up gene by gene.

Front 64

In the experiment by Yoshinori Watanabe and colleagues regarding the role of the protein shugoshin, their hypothesis was that __________. ( Concept 13.3)

Back 64

Your Answer:the protein shugoshin protects cohesins from being degraded
Correct. This hypothesis might be tested in many ways with different predictions and different controls.

Front 65

An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis? ( Concept 13.3)

Back 65

Your Answer:4
Correct. Because of the synapsis of homologous chromosomes, the number of tetrads in meiosis I will be the same as the haploid number of chromosomes.

Front 66

Which event occurs only during prophase I of the first meiotic division? ( Concept 13.3)

Back 66

Your Answer:Synapsis of homologous pairs occurs.
Correct. Synapsis of homologous chromosomes occurs at prophase of meiosis I.

Front 67

In a male mammal, every cell that undergoes meiosis gives rise to _____ sperm. ( Concept 13.3)

Back 67

Your Answer:four
Correct. One diploid parent cell gives rise to four haploid sex cells at the completion of the two meiotic divisions.

Front 68

Which one of the following occurs in meiosis, but not mitosis? ( Concept 13.3)

Back 68

Your Answer:Homologous chromosomes separate.
Correct. Homologous chromosomes separate during anaphase I. This event follows synapsis, an event unique to prophase I.

Front 69

Which function makes meiosis lengthier and more complex than mitosis? ( Concept 13.3)

Back 69

Your Answer:all of the above
Correct. Meiosis involves two divisions that typically result in four daughter cells (instead of two). Each cell has half the number of chromosomes of the original parent cell, and is, of course, not genetically identical to the parent cell.

Front 70

Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8? ( Concept 13.4)

Back 70

Your Answer:16
Correct. The number of combinations possible when chromosomes assort independently into gametes during meiosis is 2n, where n is the haploid number of chromosomes.

Front 71

Which of the following contributes to genetic variation in sexually reproducing species? ( Concept 13.4)

Back 71

Your Answer:random fertilization, independent assortment, crossing over
Correct. These three aspects of sexual reproduction increase genetic variation.

Front 72

In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing _____ different types of gametes. ( Concept 13.4)

Back 72

Your Answer:223
Correct. For each gamete there are two possibilities for each chromosome (the paternal or the maternal chromosome), and there are 23 different chromosomes per gamete.

Front 73

The diploid number of chromosomes in a certain animal is 8 (2n = 8). How do the four pairs of homologous chromosomes align and separate during meiosis? ( Concept 13.4)

Back 73

Your Answer:They align and assort independently to form any of 16 different combinations.
Correct. Because each pair of homologous chromosomes is positioned independently in metaphase I, the first meiotic division results in the independent assortment of paternal and maternal chromosomes into daughter cells. In a case in which 2n = 8, 16 combinations of chromosomes are possible for gametes.

Front 74

In a diploid set of chromosomes, one member of each pair of homologous chromosomes is derived from the father (paternal), and the other comes from the mother (maternal). If 2n = 6, what is the probability of obtaining a gamete in which all the chromosomes are paternal ones? ( Concept 13.4)

Back 74

Your Answer:1/8
Correct. The chance of any one paternal chromosome ending up in a particular gamete is 1/2, so the chance that all three would be of paternal origin would be (1/2)n, where n = 3.

Front 75

The major contribution of sex to evolution is that _____. ( Concept 13.4)

Back 75

Your Answer:The second and third answers are correct.
Correct Answer:it provides a method to increase genetic variation