Ch 13

Which of these cells is (are) haploid?

After Meiosis I and Meiosis II (C &D)

Which of these gametes contains one or more recombinant chromosomes?

B & C (composed of material derived from BOTH parents)

Which of these gametes contain one or more recombinant chromosomes?

B, C, F, & G (contain chromosomes from each parent)

Two sister chromatids are joined at the centromere prior to meiosis. Which statement is correct?

Barring mutation, the two sister chromatids must be identical.

Which of the following results when homologous chromosomes cross over in meiosis?

Corresponding segments of non-sister chromatids are exchanged.

Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II?

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.

Genes are made of _____ and encode heritable characteristics called ______ and each have a ____

DNA; traits; locus

Which diagram represents anaphase I of meiosis?

Diagram I

Look at the cell in the figure. Based on this figure, which of the following statements is true?

Diploid cell (two copies of each chromosome)

Which of the following processes occur during meiosis but not mitosis?

Diploid cells form haploid cells.

Which of the following statements describes one characteristic of each chromosome in a cell during the entire process of meiosis I?

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

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.

A (hypothetical) diploid organism has different genes that control wing color and wing length. A female of this species has a paternal chromosome set containing one orange-wing allele and one long-wing allele and a maternal set containing one blue-wing allele and one short-wing allele. Which of the following types of eggs would she be expected to produce after meiosis?

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

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

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.

Which of the following events happens at the conclusion of meiosis I?

Homologous chromosomes of a pair are separated from each other.

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.

Which of the following statements about reproduction is correct?

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

Which of the following statements about the human X chromosomes is correct?

It carries genes that influence an individual's biological sex.

A cell has completed meiosis I and the first cytokinesis, and is just beginning meiosis II. Which of the following statements describes its genetic contents?

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

Which of the following statements correctly describes a karyotype?

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

A particular organism has 46 chromosomes in its karyotype. Which of the following statements is correct regarding this organism?

It produces gametes with 23 chromosomes.

Human gametes are produced by _____.

Meiosis (produces haploid gametes from a diploid parental cell)

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.

Synapsis occurs during _____.

Prophase I (pairing of homologous chromosomes)

Which of the following phases make up the stages of mitosis?

Prophase, prometaphase, metaphase, anaphase, and telophase (*not cytokenesis!)

Genetic variation leads to genetic diversity in populations and is the raw material for evolution. Which of the following statements best represents the connection between reproduction and evolution?

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

How does natural selection apply to sexual reproduction as opposed to asexual reproduction?

Sexual reproduction results in new gene combinations, some of which will have increased reproductive fitness.

Which of the following statements describes a major difference between mitosis and meiosis I in a diploid organism?

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

Which of the following statements describes the chromosomal makeup of each daughter cell after telophase of meiosis I?

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

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.

The somatic cells of a particular plant 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?

The genes on this plant's largest chromosome are significantly different than those on the largest human chromosome.

What must happen to a chromosome before a cell starts mitosis?

The single DNA molecule in the chromosome must be replicated.

This chromosome has two chromatids, joined at the centromere. What process led to the formation of the two chromatids?

The two chromatids were formed by duplication of a chromosome.

If crossing over did not occur, which of the following statements about meiosis would be true?

There would be less genetic variation among gametes.

Which diagram represents anaphase II of meiosis?

V

A human cell containing 22 autosomes and a Y chromosome is

a sperm

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?

about 8 million

Which of the following events characterizes metaphase of mitosis?

alignment of the chromosomes at the equator

Which of the following processes will most likely produce a human zygote with 45 chromosomes?

an error during anaphase II while the sperm was produced

During which of the following phases of meiosis do homologous chromosomes separate?

anaphase I

Homologous chromosomes migrate to opposite poles during _____.

anaphase I

During which of the following phases of meiosis do centromeres split and sister chromatids migrate to opposite poles of the cell?

anaphase II

During _____ sister chromatids separate.

anaphase II (anaphase II is essentially the same as mitotic anaphase except that the cell is haploid)

DNA when complexed with protein is called?

chromatin

crossing over occurs at the ends of __________, rather than near the centromeres.

chromosomes

the start of meiosis I

chromosomes are duplicated and lined up by homologous pair.

Which processes lead to most genetic variation in sexually reproducing organisms?

crossing over, random fertilization, independent assortment of chromosomes in meiosis

During which of the following processes do sister chromatids separate from each other?

during both mitosis and meiosis II (anaphase & anaphase II)

Heritable variation is required for which of the following?

evolution

heredity & genetic variation are influenced by...

fertilization, DNA replication, crossing over, metaphase I -> anaphase I, and metaphase II -> anaphase II.

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

Meiosis II typically produces _____ cells, each of which is _____.

four; haploid

Identify all possible products of meiosis in plant and animal life cycles.

gametes (animals) and spores (plants)

Which of the following processes best describes the mechanism of gamete production in plants?

gametophytes produce gametes by mitosis

As a result of crossing over, sister chromatids are no longer ________ to each other.

identical

meiosis I is the only time that chromosomes ___________________

line up by homologous pairs

Genetic variation occurs when chromosomes are shuffled in fertilization and what other process?

meiosis (includes independent assortment & crossing over)

Crossing over of chromosomes normally takes place during which of the following processes?

meiosis I

The two homologs of a pair move toward opposite poles of a dividing cell during

meiosis I

During which of the following processes does independent assortment of chromosomes occur?

meiosis I only

Homologous pairs of chromosomes are lined up independently of other such pairs during _____.

metaphase I

During which of the following processes do homologous pairs of chromosomes align adjacent to one another at the metaphase plate of a cell?

metaphase I of meiosis

During _____ chromosomes align single file along the equator of a haploid cell.

metaphase II *haploid cell

Asexual reproduction occurs during which of the following processes?

mitosis

Crossing over occurs between _____

non-sister chromatids within a homologous pair of chromosomes

Crossing over, resulting in an increase in genetic variation, occurs between _____.

nonsister chromatids of homologous chromosomes

Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?

ovum: female cells answer = 2

centromere

point of attachment between two sister chromatids of a duplicated chromosome

Asexual reproduction __________.

produces offspring genetically identical to the parent

Which of the following processes has just occurred when chiasmata can first be viewed under a microscope?

prophase I

For crossing over to occur, homologous chromosomes must align precisely early in _______ so that nonsister chromatids can exchange corresponding segments of DNA.

prophase I. (chromosomes loosely pair up along their lengths)

During _____ a spindle forms in a haploid cell.

prophase II *haploid

Which of the following processes facilitates the fastest way for animal species to adapt to a changing environment?

sexual reproduction

Meiosis II is similar to mitosis in that

sister chromatids separate during anaphase.

In alternation of generations, what is the diploid stage of a plant that follows fertilization called?

sporophyte (diploid, multicellular stage of the plant during meiosis)

Which of the following occurs during meiosis, but not during mitosis?

synapsis (pairing of homologous chromosomes during prophase I)

Which of the following processes occurs in meiosis but not in mitosis?

synapsis of chromosomes

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

telophase I *haploid cells, TWO sister chromatids)

At the end of _____ and cytokinesis there are four haploid cells.

telophase II

Which of the following phrases defines the term genome?

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

Which of the following answers describes the phenomenon of crossing over in meiosis?

the exchange of homologous portions of nonsister chromatids (results in new combinations of genetic material)

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

In a typical animal, mitosis produces _________, while meiosis produces____________.

two diploid daughter cells; four haploid daughter cells

Meiosis I produces _____ cells, each of which is _____.

two; haploid (for Meiosis ONE!)

If the DNA content of a diploid cell is x in the G1 phase of the cell cycle and 2x at metaphase of meiosis I, then the DNA content of the same cell at metaphase of meiosis II will be

x

If a hypothetical organism has 5 chromosomes in one of its gametes, it must have ____ chromosomes in a body cell

10

A diploid organism whose somatic (nonsex) cells each contain 32 chromosomes produces gametes containing _____ chromosomes.

16 (half)

In human gamete production there is an average of _____ crossover events per chromosome pair.

2-3

Normal human gametes carry _____ chromosomes.

23

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

2x

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 (x2 for parents)

What number and types of chromosomes are found in a human somatic cell?

44 autosomes and 2 sex chromosomes (22 PAIRS of autosomes), (2 sex chromosomes: XX or XY)

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).