Chapter 11: Meiosis and Sexual Reproduction

These flashcards cover the fundamental concepts of meiosis and sexual reproduction, focusing on the processes, differences between meiosis and mitosis, life cycles of organisms, and genetic variation.

What is the primary purpose of meiosis?

To reduce the number of chromosomes from diploid (2n) to haploid (1n) gametes, while introducing genetic diversity.

What are the main differences between meiosis and mitosis?

Meiosis involves two rounds of cell division and reduces chromosome number, while mitosis is a single division that produces genetically identical cells.

What is a diploid-dominant life cycle?

A life cycle in most animals where the only haploid cells produced are the gametes, and there's no multicellular haploid stage.

What happens during prophase I of meiosis?

Homologous chromosomes pair to form tetrads, and crossing over occurs at the chiasmata.

What is crossing over?

The exchange of genetic material between nonsister chromatids during prophase I, increasing genetic variation.

Explain independent assortment.

During metaphase I, homologous chromosomes align randomly, leading to varied combinations in gametes.

What occurs in anaphase I of meiosis?

Homologous chromosomes are pulled apart, breaking the chiasmata while sister chromatids remain attached.

How does cytokinesis differ in animal and plant cells during meiosis?

Animal cells undergo cytokinesis through a cleavage furrow, while plant cells form a cell plate.

What is nondisjunction?

The failure of homologous chromosomes or sister chromatids to separate properly during meiosis, resulting in abnormal chromosome numbers.

Define aneuploidy.

An error in chromosome number, which can involve either monosomy (loss of a chromosome) or trisomy (gain of an extra chromosome).

What is the most common trisomy, and what condition does it lead to?

Trisomy 21, which leads to Down Syndrome.

What are gametophytes?

Haploid multicellular plants that produce gametes in the alternation of generations life cycle.

What is a karyotype?

The number and appearance of an individual's chromosomes, including size, banding patterns, and centromere position.

What triggers the need for meiosis in sexual reproduction?

The need to reduce chromosome number to avoid doubling in every generation.

What key life cycle types exist among sexually reproducing multicellular organisms?

Diploid-dominant, haploid-dominant, and alternation of generations.

What is the significance of sexual reproduction in terms of genetic diversity?

By mixing chromosomes from two parents, sexual reproduction increases genetic diversity within populations.