Biology Chapter 10: Meiosis

The process of fusing two gametes (sex cells), restoring the original chromosome number in a zygote.

A special type of cell division that produces four haploid daughter cells, each containing half the original number of chromosomes.

Cells with half the number of chromosomes as a diploid cell, containing only one set of chromosomes.

Containing two sets of chromosomes, one from each parent.

The process of separating homologous chromosome pairs during meiosis I, resulting in two haploid daughter cells.

Meiosis is a specialized cell division process that produces haploid (single-set chromosome) gametes, which are sex cells like sperm and egg.

Homologous chromosomes are pairs of chromosomes, one from each parent, that have the same genes but may have different versions (alleles) of those genes.

Haploid cells have only one set of chromosomes, while diploid cells have two sets of chromosomes. Meiosis is a process that ensures haploid gametes are produced.

The first meiotic division (Meiosis I) separates homologous chromosome pairs, resulting in two haploid daughter nuclei, each containing one chromosome (with two chromatids) from each pair.

The second division (Meiosis II) separates the chromatids of each chromosome, leading to four haploid daughter cells, each with one chromatid from each chromosome from the original diploid parent cell.

During prophase I of meiosis I, homologous chromosomes pair up and exchange genetic material (DNA) through a process called crossing over.

The process of homologous chromosomes exchanging genetic material during prophase I of meiosis I.

A site where maternal and paternal chromosomes have exchanged segments of DNA during crossing over.

The combining of alleles from different homologous chromosomes, resulting in new genetic combinations.

The maternal homologue is inherited from the mother's egg, while the paternal homologue is inherited from the father's sperm.

Proteins bind together the chromatids of homologous chromosomes, aligning them precisely for crossing over.

Crossing over typically occurs at two or three points along each pair of homologous chromosomes in human cells.

During prophase I of meiosis, spindle microtubules attach to the kinetochore regions of duplicated chromosomes.

In metaphase I, paired homologous chromosomes line up at the equator of the cell, perpendicular to the spindle. This is different from mitosis, where homologous chromosomes line up independently.

During metaphase I, the attachment of microtubules to each member of a homologous pair is random. This means that a daughter cell can receive any combination of maternal and paternal chromosomes.

The random combining of maternal and paternal chromosomes during meiosis, leading to genetic diversity.

During anaphase I, whole duplicated chromosomes of each homologous pair separate and move to opposite poles. This is different from mitosis, where sister chromatids separate.

In anaphase I, sister chromatids of each chromosome remain attached, moving as a unit to the opposite pole. This is the key difference in chromosome behavior compared to mitosis.

Genetic recombination and independent assortment are the key factors driving the genetic diversity of haploid cells produced by meiosis.

During meiosis, homologous chromosomes separate and move to opposite poles, resulting in the formation of two haploid daughter cells. This is a key difference from mitosis, which produces two diploid daughter cells.

Two clusters of chromosomes form, each containing one duplicated member of each pair of homologous chromosomes, resulting in a haploid state for each cluster.

During Telophase I, the spindle microtubules, responsible for chromosome separation, disappear.

Cytokinesis, the division of the cytoplasm, typically happens during telophase I.

Nuclear envelopes, the membranes surrounding the nucleus, may re-form during telophase I.

Meiosis II is typically initiated immediately after telophase I, with little or no interphase.

Between meiosis I and meiosis II, chromosomes do not replicate; they remain in their duplicated state.

At the end of meiosis I, two haploid cells are produced, each containing one chromosome from each homologous pair.

Meiosis II separates sister chromatids into four daughter nuclei, resulting in four haploid cells.

Sister chromatids separate and move to opposite poles during this phase of meiosis II.

The final stage of Meiosis II where cytokinesis occurs, nuclear membranes reform, and chromosomes decondense, resulting in four haploid daughter cells from a single diploid cell.

Variation among individuals is essential for survival in changing environments.

Rare changes in DNA sequence that are the source of new variation.

The process of meiosis and sexual reproduction ensures genetic diversity.

The random separation of homologous chromosomes during meiosis I creates unique combinations of chromosomes in each daughter cell.

The separation of homologous chromosomes during meiosis I is random, resulting in different combinations of chromosomes in the daughter cells.

The number of possible chromosome combinations in gametes is 2n, where n is the number of homologous pairs. In humans, with 23 chromosome pairs, there are 8 million possible combinations.