10 Meiosis and Sexual Life Cycles Flashcards
Asexual reproduction _____.
produces offspring genetically identical to the parent
Only one individual makes a genetic contribution to the offspring
What number and types of chromosomes are found in a human somatic cell?
44 autosomes and 2 sex chromosomes
Human somatic cells contain 22 pairs of autosomes and either two X chromosomes (in females) or an X and a Y chromosome (in males).
How are sister chromatids and homologous chromosomes different 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.
Meiosis I produces _____ cells, each of which is _____.
two … haploid
Meiosis II typically produces _____ cells, each of which is _____.
four … haploid
prophase II
The events of prophase II are essentially the same as those of mitotic prophase except that prophase II cells are haploid.
During _____ sister chromatids separate.
anaphase II
Anaphase II is essentially the same as mitotic anaphase except that the cell is haploid.
At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.
telophase I
At the end of telophase I and cytokinesis, there are two haploid cells with chromosomes that consist of two sister chromatids each.
Synapsis occurs during _____.
prophase I
Synapsis, the pairing of homologous chromosomes, occurs during prophase I.
Homologous chromosomes migrate to opposite poles during _____.
anaphase I
During anaphase I sister chromatids remain attached at their centromeres, and homologous chromosomes move to opposite poles.
During _____ chromosomes align single file along the equator of a haploid cell.
metaphase II
Metaphase II is essentially the same as mitotic metaphase except that the cell is haploid.
At the end of _____ and cytokinesis there are four haploid cells.
telophase II
At the end of telophase II and cytokinesis there are four haploid cells.
During _____ a spindle forms in a haploid cell.
prophase II
Prophase II is essentially the same as mitotic prophase except that the cells are haploid.
Mitosis results in the formation of how many cells; meiosis results in the formation of how many cells?
two diploid cells … four haploid cells
In mitosis a cell that has doubled its genetic material divides to produce two diploid daughter cells. In meiosis a cell that has doubled its genetic material undergoes two rounds of division, producing four haploid cells.
Which of the following occurs during meiosis but not during mitosis?
A.Chromosomes condense.
B. Chromosomes align at the metaphase plate.
C. A spindle apparatus forms.
D. Synapsis occurs.
E. Chromosomes migrate to opposite poles.
Synapsis occurs.
The pairing of homologous chromosomes that only occurs during prophase I of meiosis is called synapsis.
What is crossing over?
the exchange of homologous portions of nonsister chromatids
The result is new combinations of genetic material (genetic recombination).
Genetic variation occurs when chromosomes are shuffled in fertilization and what other process?.
meiosis
Variation is produced as a result of independent assortment and crossing over.
Heritable variation is required for which of the following?
evolution
Variation is the raw material of evolution.
A human cell containing 22 autosomes and a Y chromosome is
a sperm.
Homologous chromosomes move toward opposite poles of a dividing cell during
meiosis I
Meiosis II is similar to mitosis in that
sister chromatids separate during anaphase.
What is a locus?
precise location of a gene on a chromosome
Sexual and asexual reproduction are alike in that _____.
they can both occur in multicellular organisms
A clone is the product of _____.
asexual reproduction
mitosis
A karyotype is _____.
a photograph of all of an individual’s chromosomes
Which, if any, of the following statements is true?
Diploid cells can divide by mitosis.
Diploid cells can divide by meiosis.
Haploid cells can divide by mitosis.
Haploid cells cannot divide by meiosis.
All of the above responses are correct.
All of the above responses are correct.
Which of the following is part of the life cycle called alternation of generations?
multicellular haploid stage (gametophyte)
multicellular diploid stage (sporophyte)
zygote
spores
all of the above
all of the above
A life cycle in which the only multicellular form is haploid is most typical of _____.
fungi
Sister chromatids are identical copies of each other formed during DNA ______
synthesis
Which of the following statements about homologous chromosomes is correct?
They are found in animal cells but not in plant cells.
They have genes for the same traits at the same loci.
They pair up in prophase II.
They are found in haploid cells.
They are found in the cells of human females but not in human males.
They have genes for the same traits at the same loci.
When we say that an organism is haploid, we mean that _____.
its cells have a single set of chromosomes
Which of the following is a function of mitosis in humans?
production of eggs
production of sperm
decreasing the number of chromosomes
multiplication of body cells
increasing genetic variability
multiplication of body cells
Somatic cells in humans contain _____ set(s) of chromosomes and are therefore termed _____.
two … diploid
Nearly all life cycles have both haploid and diploid phases. Usually, the transition from haploid to diploid takes place _____.
at fertilization, when gametes fuse
Spores and gametes are different in that _____.
gametes can fuse to form a zygote, but spores can develop into independent organisms without first forming a zygote
Which of the following results in cells that contain half the parental chromosome number?
meiosis
The two cell divisions of meiosis, I and II, produce __haploid daughter cells.
four
At the end of telophase I of meiosis and the first cytokinesis, there are _____.
two haploid cells
What is the result when a diploid cell undergoes meiosis?
four haploid cells
Synapsis occurs during _____.
prophase I
Which of the following occurs during anaphase II?
Sister chromatids separate and migrate toward opposite poles.
Which of the following occurs during anaphase I?
Homologs separate and migrate toward opposite poles.
Cytokinesis is the _____.
division of one cell into two
Crossing over occurs during _____.
prophase I
Regions of chromosomes where nonsister chromatids cross over are called _____.
chiasmata
Which event occurs only during prophase I of the first meiotic division?
Synapsis of homologous pairs occurs.
Which of the following occurs in meiosis, but not mitosis?
Homologous chromosomes separate.
Which function makes meiosis lengthier and more complex than mitosis?
decreasing the chromosome number to haploid
introducing genetic variation among the daughter cells
ensuring that each daughter cell gets a single, complete set of chromosomes
undergoing two rounds of cytokinesis
all of the above
all of the above
Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?
16
The major contribution of sex to evolution is that _____.
it provides a method to increase genetic variation
Which of the following contributes to genetic variation in sexually reproducing species?
crossing over, internal fertilization, independent assortment
independent assortment, spindle formation, random fertilization
random fertilization, DNA synthesis, independent assortment
random fertilization, independent assortment, crossing over
internal fertilization, spindle formation, crossing over
random fertilization, independent assortment, crossing over
Although _____ is nearly universal among animals, bdelloid rotifers _____.
sexual reproduction … reproduce asexually but can increase genetic variation present in a population by means of the uptake of DNA from other rotifers
