GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Meiosis

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Example Questions

Example Question #1 : Help With Meiosis

During which of the following stages of meiosis is the ploidy of the cell equal to n (haploid)?

I. Telophase I, after nuclear envelopes reform

II. Metaphase II, while chromosomes are lined up on the equatorial plate

III. Anaphase II, immediately after separation of sister chromatids

IV. Metaphase I, while chromosomes are lined up on the equatorial plate

Possible Answers:

I, II, III, and IV

I and II

I, II, and III

III and IV

Correct answer:

I and II

Explanation:

This question is a little tricky and depends entirely on the definition of when something is officially a chromosome. A sister chromatid is not officially considered a chromosome until being separated from its partner.

During metaphase I, the homologous chromosomes have yet to separate, so ploidy is still 2n (diploid). Statement IV is false.

During telophase I, the homologous chromosomes have separated and the nuclear envelopes have reformed, effectively forming two haploid nuclei during telophase I. Statement I is true.

During metaphase II, the sister chromatids are still attached, so the cells are still haploid. Statement II is true.

During anaphase II, however, immediately after the sister chromatids are separated they are now considered individual chromosomes. This effectively increases ploidy back to 2n until the nuclear envelopes reform. Statement III is false.

Example Question #2 : Help With Meiosis

A normal somatic human cell contains 46 chromosomes. During anaphase of meiosis I, prior to reformation of the nuclear envelope, how many chromosomes are present in a human cell?

Possible Answers:

Correct answer:

Explanation:

For this question it is important to know the distinction between the genetic material being separated in meiosis I versus meiosis II. During meiosis I homologous chromosomes are separated, and during meiosis II sister chromatids are separated. Reduction of ploidy therefore occurs during telophase I, after the nuclear envelope reforms (due to the segregation of homologous chromosomes). During anaphase I there are technically still 46 chromosomes in the cell, even though each contains two sister chromatids and have been pulled to different regions of the cell. The total amount of genetic material has not changed.

Note that during anaphase of meiosis II ploidy is also at 46 chromosomes. At this point, sister chromatids have been separated from each of the 23 chromosomes present, resulting in 46 separate genetic units. The cell is still considered haploid, since the homologous chromosomes are not present.

Example Question #61 : Cellular Processes

Which event takes place in meiosis, but not in mitosis?

Possible Answers:

Sister chromatids are separated from one another

The nuclear envelope reforms around the genetic material

The chromosomes align in the center of the cell

Homologous chromosomes are separated from one another

Correct answer:

Homologous chromosomes are separated from one another

Explanation:

Meiosis has many key differences from mitosis, despite the fact that both are used to divide a parent cell into daughter cells. One of the main differences is that meiosis involves the separation of homologous chromosomes, which halves the chromosome number in the daughter cells. This event does not take place in mitosis, because both daughter cells are are still diploid following division. 

Example Question #4 : Help With Meiosis

During what phase of meiosis does crossing over occur?

Possible Answers:

Prophase II

Metaphase I

Prophase I

Telophase I

Correct answer:

Prophase I

Explanation:

Meiosis results in genetically unique daughter cells due to the event of crossing over and the phenomenon of independent assortment. Crossing over takes place during prophase I when the homologous chromosomes come in contact with each other to form tetrads.

Example Question #5 : Help With Meiosis

Which of the following are true of meiosis?

Possible Answers:

Homologous chromosomes separate from one another in anaphase II

The centromeres separate from each other during anaphase I

Homologous chromosomes line up on the equatorial plate by the end of anaphase I

Homologous chromosomes synapse in anaphase I

Homologous chromosomes separate from one another in anaphase I

Correct answer:

Homologous chromosomes separate from one another in anaphase I

Explanation:

During anaphase I, spindle fibers form and homologous chromosomes (each consisting of two chromatids) move toward opposite poles of the cell. During anaphase II, sister chromatids separate at their centromeres and are pulled toward opposite poles of the cell. Synapsis happens during prophase I, not anaphase I, as chromosomes condense and homologs align.

Example Question #6 : Help With Meiosis

Suppose X is the amount of DNA in a mature human cell that is not actively replicating. What amount of DNA would be found in a mature cell that has fully completed meiosis?

Possible Answers:

.25X

X

4X

0.5X

2X

Correct answer:

0.5X

Explanation:

Gametes are the types of cells produced by meiosis. For example, a mature spermatozoan is a type of gamete. Adult cells are diploid, and through meiosis, gametes are haploid. Therefore, gametes have half of the genetic material of a mature cell. Thus, a gamete would be reflected with 0.5X as the amount of genetic material.

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

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