Meiosis Guided Notes for Test

Vocabulary practice flashcards covering chromosome concepts, the stages of Meiosis I and Meiosis II, genetic variation mechanisms, and comparisons between mitosis and meiosis based on the guided notes.

Meiosis

A form of cell division that reduces the number of chromosome sets by half, consisting of one round of DNA copying followed by two cell divisions to support sexual reproduction.

Gametes

Haploid sex cells produced through meiosis, such as sperm and eggs, that contain $23$ chromosomes in humans.

Diploid ($2n$)

Cells containing two sets of chromosomes, which includes most human body cells with a total of $46$ chromosomes.

Haploid ($n$)

A cell that possesses one set of chromosomes, such as a human sex cell containing $23$ chromosomes.

Homologous Chromosomes

A matching pair of chromosomes possessing the same genes at the same locations, with one chromosome inherited from each parent.

Alleles

Different versions of the same gene that can be carried on homologous chromosomes.

S Phase of Interphase

The period prior to meiosis during which DNA is copied, doubling the amount of DNA while the chromosome count remains the same.

Sister Chromatids

Two attached copies of a duplicated chromosome that remain joined at the centromere until Meiosis II.

Centromere

The region where sister chromatids stay joined together after replication, ensuring the chromosome count does not change.

Zygote

A diploid cell formed by the union of two haploid gametes during fertilization.

Tetrad

A paired structure containing four chromatids formed by homologous chromosomes pairing up during prophase I.

Crossing-Over

The exchange of DNA segments between nonsister chromatids of homologous chromosomes during prophase I, creating new allele combinations and increasing genetic variation.

Metaphase I

The stage of meiosis where homologous chromosome pairs line up along the middle of the cell.

Anaphase I

The stage of meiosis I where homologous chromosomes separate and move toward opposite poles while sister chromatids remain attached.

Cytokinesis

The division of a cell's cytoplasm that occurs following nuclear division.

Prophase II

The stage where a new spindle forms in each haploid cell and spindle fibers help move the chromosomes.

Metaphase II

The stage of meiosis II during which duplicated chromosomes line up individually along the middle of each cell.

Anaphase II

The stage of meiosis II where sister chromatids separate, each becoming an individual chromosome as they move apart.

Telophase II

The stage where new nuclei assemble, leading after cytokinesis to the production of four genetically distinct haploid cells.

Independent Assortment

The random orientation and alignment of each homologous pair during metaphase I, which alters the mixture of maternal and paternal chromosomes entering each gamete.

Fertilization

The random combination of sperm and egg that introduces further genetic variation after meiosis and restores the diploid chromosome number.

Chromosome Reduction

The halving of chromosome sets during meiosis that prevents the chromosome count from doubling across successive generations upon gamete fusion.

Mitosis

Cell division supporting growth and tissue repair that yields two genetically similar cells, in contrast to meiosis which yields four genetically diverse haploid cells.

Nondisjunction

An error wherein homologous chromosomes or sister chromatids fail to separate properly during division, resulting in daughter cells with abnormal chromosome numbers.