Chapter 13 Meiosis and sexual life cycles Flashcards
In meiosis, __________ of __________ cross over and form __________.
nonsister chromatids; homologous pairs; chiasmata
Which of the following is a function of mitosis in humans?
Multiplication of body cells
Which of the following statements about homologous chromosomes is correct?
They have genes for the same traits at the same loci.
The process called __________ reduces the chromosome number by __________.
meiosis; two consecutive cell divisions
Which life cycle stage is found in plants but not animals?
Multicellular haploid
A pair of genetic structures carrying genes that control the same inherited characters are called __________.
homologous chromosomes
A life cycle in which the only multicellular form is haploid is most typical of __________.
fungi
Allelic variation is an important source of __________ in a population.
genetic diversity
What is the result when a diploid cell undergoes meiosis?
Four haploid cells
Genetic diversity requires __________.
sexual reproduction, independent assortment, crossing over between nonsister chromatids of homologous chromosomes, and random fertilization
Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?
16
Characteristic of the bdelloid rotifer is that it __________.
is an example of an animal that has not reproduced sexually in 40 million years
Which of the following occurs in meiosis, but not mitosis?
Homologous chromosomes separate.
What is a locus?
The precise location of a gene on a chromosome.
Somatic cells in humans differs from gametes in that human somatic cells __________.
contain two sets of each of the 23 chromosome types
Regarding the role of cohesin protein in maintaining cohesion between sister chromatids, which of the following statements is false?
During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms.
The life cycle called __________ in plants has two multicellular stages: the __________ and the __________.
alternation of generations; haploid gametophyte; diploid sporophyte
At the end of mitosis, __________ daughter cells that are genetically __________ are formed, while at the end of meiosis, __________ daughter cells that are genetically __________ are formed.
two; identical; four; distinct
How many genes are present in the human genome?
Tens of thousands
Sister chromatids differ from nonsister chromatids in that sister chromatids __________.
are products of the S phase of the cell cycle and are two copies of one chromosome
The major contribution of sex to evolution is that __________.
it provides a method to increase genetic variation
__________ are a group of genetically identical individuals produced by a process called __________.
Clones; asexual reproduction
Unless the chromosomes were stained to show band patterns, a karyotype would be least likely to show which of the following?
Part of a chromosome turned around.
A clone is the product of __________.
asexual reproduction and mitosis
Darwin realized the importance of heritable variation to evolution __________.
even though he never read any of Gregor Mendel’s work
Somatic cells in humans contain __________ set(s) of chromosomes and are therefore termed __________.
two; diploid
The zipper-like complex that forms in meiosis occurs during __________ and is called the __________.
prophase I; synaptonemal complex
The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?
44
Somatic cells in animals differ from gametes in that somatic cells __________.
are all of the cells of the body except for the gametes and their precursors
What must happen to a chromosome before a cell starts mitosis?
The single DNA molecule in the chromosome must be replicated.
Which of the following phases make up the stages of mitosis?
Prophase, prometaphase, metaphase, anaphase, and telophase
Which of the following events characterizes metaphase of mitosis?
alignment of the chromosomes at the equator
Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms (pg) per nucleus. During the entirety of which stage of the cell cycle did the nucleus contain 6 pg of DNA?
G2
Asexual reproduction __________.
produces offspring genetically identical to the parent
What number and types of chromosomes are found in a human somatic cell?
44 autosomes and 2 sex chromosomes
For what purpose(s) might a karyotype be prepared?
for prenatal screening, to determine if a fetus has the correct number of chromosomes
to determine whether a fetus is male or female
to detect the possible presence of chromosomal abnormalities such as deletions, inversions, or translocations
In alternation of generations, what is the diploid stage of a plant that follows fertilization called?
sporophyte
Human gametes are produced by _____.
meiosis
Normal human gametes carry _____ chromosomes.
23
A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.
16
Meiosis I produces _____ cells, each of which is _____.
two … haploid
Meiosis II typically produces _____ cells, each of which is _____.
four … haploid
During _____ sister chromatids separate.
anaphase II
At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
telophase I
Synapsis occurs during _____.
prophase I
Homologous chromosomes migrate to opposite poles during _____.
anaphase I
During _____ chromosomes align single file along the equator of a haploid cell.
metaphase II
At the end of _____ and cytokinesis there are four haploid cells.
telophase II
During _____ a spindle forms in a haploid cell.
prophase II
Which of the following statements correctly describes how sister chromatids and homologous chromosomes differ from each other?
Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.
In a typical animal, mitosis produces _________, while meiosis produces____________.
two diploid daughter cells, four haploid daughter cells
Which of the following occurs during meiosis, but not during mitosis?
synapsis occurs
Which of the following answers describes the phenomenon of crossing over in meiosis?
the exchange of homologous portions of nonsister chromatids
A cell in prophase I has a diploid number (2n) of 36. At the end of meiosis II, how many sets of chromosomes will each gamete have?
1 set of chromosomes for a total of 18 chromosomes
Which statement correctly describes the chromosomes in each daughter cell at the end of meiosis I?
The sister chromatids of each duplicated chromosome are no longer identical.
The parent cell just before prophase I is
Diploid
The daughter cells at the end of meiosis II are
Haploid
Each daughter cell at the end of meiosis I has _____
of the DNA present in the parent cell just before prophase I.
one half
Each daughter cell at the end of meiosis II has ______
of the DNA present in the parent cell just before prophase I.
one quarter
Homologous pairs of chromosomes are lined up independently of other such pairs during _____.
metaphase I
Crossing over, resulting in an increase in genetic variation, occurs between _____.
nonsister chromatids of homologous chromosomes
In human gamete production there is an average of _____ crossover events per chromosome pair.
2–3
Genetic variation occurs when chromosomes are shuffled in fertilization and what other process?
meiosis
Heritable variation is required for which of the following?
evolution
If a plant biologist succeeds in generating a single plant with a particularly desirable flower, which of the following approaches would be the most efficient way to generate more plants with this trait?
Clone the plant
Asexual reproduction occurs during which of the following processes?
mitosis
Quaking aspen trees usually reproduce by extending underground stems that then push aboveground and grow into trees. 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?
38
Which of the following statements about reproduction is correct?
In asexual reproduction, offspring are produced by fertilization without meiosis.
Which of the following statements is true of a species that has a chromosome number of 2n = 16?
Each diploid cell has eight homologous pairs of chromosomes.
Which of the following processes best describes the mechanism of gamete production in plants?
gametophytes produce gametes by mitosis.
Which of the following statements describes an example of alternation of generations?
A diploid plant (sporophyte) produces a spore by meiosis that gives rise to a multicellular, haploid pollen grain (gametophyte).
A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism?
Its gametes must have 23 chromosomes.
Which of the following statements best describes homologous chromosomes?
They carry information for the same traits.
Many diploid organisms produce haploid gametes for reproduction. Which of the following best describes how the diploid number of chromosomes is restored in the offspring of these organisms?
fertilization combines chromosomes from each parent into resulting zygote
Which of the following statements correctly describes a karyotype?
It is an organized image of a cell’s chromosomes.
How do cells at the completion of meiosis compare with cells that are in prophase of meiosis I?
The cells have half the number of chromosomes and one-fourth the amount of DNA.
Which of the following events happens at the conclusion of meiosis I?
Homologous chromosomes of a pair are separated from each other.
During which of the following processes do sister chromatids separate from each other?
during both mitosis and meiosis II
Which of the following processes occurs in meiosis but not in mitosis?
synapsis of chromosomes
Which of the following processes has just occurred when chiasmata can first be viewed under a microscope?
prophase 1
During which of the following phases of meiosis do homologous chromosomes separate?
anaphase I
Which of the following statements describes a major difference between meiosis II and mitosis in a diploid animal?
Meiosis II occurs in a haploid cell, while mitosis occurs in diploid cells.
Crossing over of chromosomes normally takes place during which of the following processes?
meiosis I
During which of the following phases of meiosis do centromeres split and sister chromatids migrate to opposite poles of the cell?
anaphase II
Which of the following explanations correctly describes a reproductive approach?
In asexual reproduction, a single individual is the sole parent and passes copies of its genes to its offspring without the fusion of gametes.
During which of the following processes does independent assortment of chromosomes occur?
in meiosis I only
Independent assortment of chromosomes is a result of which of the following processes?
the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I
Which of the following results when homologous chromosomes cross over in meiosis?
Corresponding segments of non-sister chromatids are exchanged.
