Lect 15 - cell division- meiosis

Flashcards about cell division with emphasis on meiosis.

What is Meiosis?

Cell division in sexually reproducing organisms, involving two rounds of division but only one of DNA replication, resulting in 4 haploid cells.

What happens during Meiosis I?

Homologous pairs of chromosomes are separated.

What are the key events during Prophase I of Meiosis?

Nuclear envelope breaks down, chromosomes condense, spindle forms, crossing over occurs at the chiasmata.

What are the key events during Metaphase I of Meiosis?

Chromosomes attach to kinetochore microtubules, homologous chromosomes line up independently.

What occurs during Anaphase I of Meiosis?

Recombined homologous chromosomes separate, sister chromatids remain attached.

What occurs during Telophase I of Meiosis?

Duplicated chromosomes reach poles, spindle disappears, nuclear envelope reforms.

What occurs during Cytokinesis I of Meiosis in animal cells?

Formation of a cleavage furrow which pinches the cell into two, resulting in two haploid cells each with duplicated chromosomes.

What happens during Meiosis II?

Sister chromatids are separated.

What occurs during Prophase II of Meiosis?

Spindle forms, kinetochore microtubules attach to duplicated chromosomes.

What occurs during Metaphase II of Meiosis?

Duplicated chromosomes align at the metaphase plate.

What occurs during Anaphase II of Meiosis?

Sister chromatids disjoin, becoming independent daughter chromosomes that move to opposite poles.

What occurs during Telophase II & Cytokinesis of Meiosis?

Two daughter nuclei form, producing four genetically distinct haploid daughter cells.

What are the main sources of genetic diversity within sexual reproduction?

Independent assortment of chromosomes, crossing over, random fertilization of gametes.

Why is genetic diversity important?

Allows selective responses to spatially variable, changing environments, and sib-sib competition.