AP Biology : Understanding Meiosis

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #11 : Understanding Meiosis

Cells containing only one homologue of each chromosome would be produced following which of the following processes?

Possible Answers:

Mitosis

Meiosis I

S phase

Both meiosis I and mitosis

Correct answer:

Meiosis I

Explanation:

For this question, remember that a cell containing only one homologue is a haploid cell. Cells containing two homologous chromosomes are considered diploid.

Following the S phase and mitosis, the cells are diploid because they contain pairs of homologous chromosomes.

Following meiosis I, however, the daughter cells are haploid because they contain only one homologue. These homologues still consist of two identical sister chromatids, which will be separated following meiosis II, but the halving of genetic material during meiosis I still generates haploid daughter cells.

Example Question #12 : Understanding Meiosis

Which of the following is true regarding meiosis I and meiosis II?

Possible Answers:

Both involve reductional division

The G2 phase precedes both

Sister chromatids separate in anaphase of meiosis I, but not in meiosis II

Both produce haploid cells

Correct answer:

Both produce haploid cells

Explanation:

Meiosis I involves the separation of homologous chromosomes, while meiosis II involves the separation of sister chromatids. The G2 phase precedes meiosis I or mitosis, but does no precede meiosis II. Interkinesis is the period that separates meiosis I and meiosis II.

Meiosis I results in two daughter cells, each with only one copy of each chromosome, from a parent cell with two copies of each chromosome. The parent cell is diploid, while the daughter cells are haploid. This is known as reductional division because the daughter cell contain less genetic material than the parent cell. Meiosis II results in four daughter cells from two parent cells. Each parent contains one copy of each chromosome, and each daughter cell also contains one copy of each chromosome (although the material is stored on a single chromatid). Since both parent and daughter cells contain the same amount of genetic information, this is considered an equational division. The daughter cells of both meiosis I and meiosis II contain only one copy of each chromosome, as homologous pairs have been separated. Both meiosis products are thus considered haploid, making this the correct answer.

Example Question #13 : Understanding Meiosis

How many chromosomes does a human germ cell contain during metaphase I and telophase II, respectively?

Possible Answers:

There are 23 chromosomes during metaphase I and 23 chromosomes during telophase II

There are 46 chromosomes during metaphase I and 46 chromosomes during telophase II

There are 23 chromosomes during metaphase I and 46 chromosomes during telophase II

There are 46 chromosomes during metaphase I and 23 chromosomes during telophase II

Correct answer:

There are 46 chromosomes during metaphase I and 46 chromosomes during telophase II

Explanation:

For this question you have to carefully track the chromosomes through meiosis. A human cell in metaphase I will have formed the tetrads and would have aligned the genetic material along the metaphase plate. The sister chromatids are still attached to one another, so they only count as one chromosome per pair of chromatids. There are a total of 46 chromosomes in metaphase I, each comprised of two sister chromatids. There are 23 homologous pairs, each containing two complete chromosomes.

During telophase II, the cell is in a haploid state. The homologous pairs have been separated during anaphase I, such that each cell contains 23 complete chromosomes. Each chromosome is then broken into its chromatids, such that the total number of chromosomes represented during anaphase II is 46, with each chromatid representing a chromosome. If each of the chromosomes still had its sister chromatid, then the total number of chromosomes would be 23. Telophase II follows anaphase II. The 46 chromatids are sequestered to opposite sides of the cell, but the cell has not yet divided. A cell in telophase II is haploid, containing only one copy of each homologous chromosome, but contains two chromatids for each copy. The total number of chromosomes in a telophase II cell is thus 46. As soon as the cell completes cytokinesis, and two daughter cells are formed, they become haploid cells with 23 chromosomes each.

Example Question #11 : Understanding Meiosis

In vertebrates, sperm cells typically contribute which of the following a new organism?

Possible Answers:

A complete zygote

Diploid sex chromosomes

All of the cytoplasm of the zygote

A complementary haploid portion of chromosomes

Nuclei

Correct answer:

A complementary haploid portion of chromosomes

Explanation:

In most vertebrates, sperm cells join with egg cells to form a zygote. Each cell produces a haploid complement of chromosomes in order to form the zygote. The result is a new organism with a full set of maternal chromosomes and a full set of paternal chromosomes.

When a sperm joins with an egg, only the nucleus of the sperm enters to egg to form the zygote. The nuclear envelope is then altered, allowing the paternal DNA to intermix with the maternal DNA in the zygote nucleus. The sperm does not contribute a nucleus (only genetic material), cytoplasm, or diploid copies of any chromosome.

Example Question #111 : Cellular Division

Of the following choices, which most accurately describes the cells produced from the process of meiosis?

Possible Answers:

The cells are genetically identical to the parental cells

The cells are genetically unique from the parental cells

The cells are diploid

The cells are genetically identical to all other cells in the human body

The cells are used in the repair of tissues

Correct answer:

The cells are genetically unique from the parental cells

Explanation:

Reductional division of cells occurs during meiosis. This means that the number of chromosomes in the cells undergoing meiosis is reduced by half, as compared to the parental cells. The cells that arise from meiosis are genetically unique from their parental cells, since they do not retain the same genetic information.

The cells that result from meiosis are haploid, carrying only half of the normal DNA present in somatic cells.

Example Question #12 : Understanding Meiosis

Which of the following is a way in which meiosis increases genetic diversity?

Possible Answers:

Recombination

Separation of sister chromatids

Inducing genetic mutations

Chromosome condensation

Correct answer:

Recombination

Explanation:

Crossing over, or recombination, is a phenomenon in which small parts of homologous chromosomes move from one copy of the chromosome to the other. This process helps promote genetic diversity by providing slightly different copies of chromosomes for offspring.

Inducing genetic mutations would be a way to increase diversity, but it is not something that actually happens during meiosis. Condensation of chromosomes and separation of sister chromatids occur during both mitosis and meiosis, and do not promote genetic diversity.

Example Question #113 : Cellular Division

What event happens in meiosis I that does not happen in meiosis II?

Possible Answers:

Telophase

Separation of sister chromatids

Separation of homologous chromosomes

Metaphase

Correct answer:

Separation of homologous chromosomes

Explanation:

In meiosis I the cell separates homologous chromosomes. In meiosis II the cell separates sister chromatids. In general, meiosis I and II are similar processes that go through the same steps (prophase, metaphase, etc.) with only a few key difference. During metaphase I, homologous chromosomes line up in tetrads. During metaphase II, chromosomes line up singularly. Crossing over can only occur during the formation of tetrads, and cannot occur during meiosis II.

Example Question #114 : Cellular Division

In multicellular eukaryotes, there are two distinct cell types: germ cells and somatic cells. Which of the following is characteristic of germ cells?

Possible Answers:

They are haploid

They produce gametes

They only undergo meiosis

They are a special type of somatic cell

They only undergo mitosis

Correct answer:

They produce gametes

Explanation:

Germ cells are diploid stem cells that give rise to the gametes of organisms that reproduce sexually. These cells can undergo both meiosis and mitosis. Mitosis is used to duplicate the germ cell, while meiosis is used to generate gametes.

Somatic cells are found in all other regions of the body, and are only capable of mitosis.

Example Question #11 : Understanding Meiosis

In which phase of meiosis does crossing over occur?

Possible Answers:

Telophase I

Metaphase I

Prophase II

Anaphase I

Prophase I

Correct answer:

Prophase I

Explanation:

Crossing over occurs during prophase I of meiosis I. Crossing over is the physical exchange of chromosome parts, resulting in recombinant chromosomes and increased genetic variability. In order for this to occur, there is a requirement that the two homologous chromosomes be aligned next to one another, which occurs in prophase I of meiosis during tetrad formation.

Example Question #116 : Cellular Division

A scientist is dissecting a female fetal pig and takes a tissue sample from its ovaries. The scientist places the tissue sample on a slide and examines the eggs in the ovarian tissue. At what stage in the cell cycle are these germ cells?

Assume that oogenesis in the fetal pig is the same as in a human.

Possible Answers:

Prophase II

Metaphase II

Metaphase I

Anaphase I

Prophase I

Correct answer:

Prophase I

Explanation:

Prophase I is the correct answer. During oogenesis in mammals, meiosis I occurs during the prenatal age. When the germ cells reach prophase I, the cell cycle is arrested, and the cells are frozen in prophase until puberty.

During puberty, the female will begin to ovulate. This means that one egg cell will progress from prophase I to metaphase I and complete meiosis on a cyclical basis, known as the menstrual cycle.

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