Mastering Biology Chapter 13 Flashcards

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Questions and Answers

Human gametes are produced by ____.

meiosis

Normal human gametes carry _____ chromosomes.

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

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. Signup and view all the answers

Which of these cells is (are) haploid?

Cell C Signup and view all the answers

What is crossing over?

The exchange of genetic material between nonsister chromatids of homologous chromosomes. Signup and view all the answers

What are recombinant chromosomes?

Chromosomes created when crossing over combines DNA from two parents. Signup and view all the answers

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

two, haploid Signup and view all the answers

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

four, haploid Signup and view all the answers

What occurs during prophase II?

Nuclear envelope breaks down, and chromosomes condense. Signup and view all the answers

What happens during anaphase II?

Sister chromatids separate and migrate to opposite poles. Signup and view all the answers

What occurs in telophase II and cytokinesis?

Nuclei form at opposite poles and cytokinesis splits the cells apart. Signup and view all the answers

During _____ sister chromatids separate.

anaphase II Signup and view all the answers

What happens during telophase I and cytokinesis?

Two haploid daughter cells are produced. Signup and view all the answers

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

telophase I Signup and view all the answers

What begins during prophase I?

Condensation of the chromosomes and pairing of homologous chromosomes. Signup and view all the answers

What occurs during metaphase II?

Chromosomes align on the metaphase plate. Signup and view all the answers

What happens during metaphase I?

Chromosome tetrads are aligned on the metaphase plate. Signup and view all the answers

Synapsis occurs during _____.

prophase I Signup and view all the answers

Homologous chromosomes migrate to opposite poles during _____.

anaphase I Signup and view all the answers

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

metaphase II Signup and view all the answers

Study Notes

Meiosis Basics

Human gametes are produced through meiosis, leading to haploid cells from a diploid origin.
Normal human gametes contain 23 chromosomes.
A diploid organism with 32 chromosomes produces gametes with 16 chromosomes, half the diploid number.

Meiosis Stages

Meiosis I reduces DNA content from diploid to haploid; it halves the ploidy level.
Meiosis II maintains the haploid state of cells; DNA content does not change.

Cell Types and Quantity

After both meiosis I and II, the resulting cells are haploid.
Meiosis I produces two haploid cells, while meiosis II typically results in four haploid cells.

Genetic Variation

Crossing over occurs during prophase I, allowing the exchange of genetic material between homologous chromosomes.
Recombinant chromosomes derive from crossing over, merging DNA from both parents into a single chromosome.

Phases of Meiosis

Prophase I involves chromosome condensation, synapsis of homologous chromosomes, and the formation of tetrads where crossing over occurs.
Metaphase I aligns tetrads on the metaphase plate, positioning homologous chromosomes for separation.
Anaphase I sees homologous chromosomes migrate to opposite poles, leading to the eventual formation of haploid cells.
Telophase I and cytokinesis finalize the separation, creating two haploid daughter cells, each with chromosomes made of sister chromatids.

Further Steps in Meiosis

During prophase II, chromosomes reorganize similarly to mitotic prophase, yet the cells remain haploid.
Metaphase II aligns chromosomes single-file on the metaphase plate, differing only in cell ploidy compared to mitosis.
Anaphase II involves sister chromatids separating to opposite poles, followed by telophase II, resulting in four haploid cells after cytokinesis.

Key Terms

Synapsis occurs during prophase I, forming tetrads for genetic exchange.
Sister chromatids separate during anaphase II, a crucial step in ensuring gametes receive the correct genetic information.

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Test your knowledge of Chapter 13 in Mastering Biology with these flashcards. The quiz covers essential concepts such as meiosis, the number of chromosomes in gametes, and diploid organisms. Perfect for reinforcing your understanding of human reproductive biology.