ap bio concept 10.3: Meiosis reduces the number of chromosome sets from diploid to haploid

What is the purpose of meiosis?

To create 4 genetically different haploid cells (gametes) for reproduction.

How is meiosis different from mitosis?

Meiosis has two divisions and makes 4 unique cells; mitosis has one division and makes 2 identical cells.

Why is meiosis important?

It reduces chromosome number by half and increases genetic variation.

What are homologous chromosomes?

Chromosomes of the same size and shape with similar genes but different alleles.

What happens in Interphase before meiosis begins?

Chromosomes replicate during the S phase, creating sister chromatids.

What is the main goal of Meiosis I?

To separate homologous chromosome pairs.

What is the main goal of Meiosis II?

To separate sister chromatids.

How many cells are produced at the end of meiosis?

Four genetically unique haploid cells.

What happens in Prophase I?

Homologous chromosomes pair up, and crossing over occurs.

What happens in Metaphase I?

Homologous chromosome pairs line up in the middle of the cell.

What happens in Anaphase I?

Homologous chromosomes are pulled apart to opposite poles.

What happens in Telophase I and Cytokinesis?

Two haploid cells are formed, each with duplicated chromosomes.

What happens in Prophase II?

A new spindle forms, and chromosomes prepare to line up.

What happens in Metaphase II?

Chromosomes (sister chromatids) line up in the middle of the cell.

What happens in Anaphase II?

Sister chromatids are pulled apart to opposite poles.

What happens in Telophase II and Cytokinesis?

Four haploid cells are formed, each genetically unique.

What is crossing over, and when does it happen?

Exchange of genetic material between homologous chromosomes during Prophase I.

What are haploid cells?

Cells with half the number of chromosomes (n), like sperm and eggs.

What does independent assortment mean?

Random alignment of homologous chromosomes during Metaphase I, increasing genetic diversity.

Why are the daughter cells genetically unique?

Due to crossing over and independent assortment during meiosis.

Goal of meiosis I

Halve the chromosome number by separating homologous chromosomes.

Meiosis makes..

4 genetically unique haploid cells.

Mitosis makes..

2 identical diploid cells.

Meiosis has…

two divisions, mitosis has one.

Crossing over in meiosis…

Increases genetic variation

Prophase=

Prepare (condense chromosomes, crossing over).

Metaphase=

Middle (chromosomes line up).

Anaphase=

Apart (pull chromosomes or chromatids apart).

Telophase=

Two (nuclei form).

Meiosis I is the

reductional division because it halves the number of chromosome sets per cell from diploid to haploid (2n to n)

Meiosis II is the

equational division because the haploid cells divide to produce haploid daughter cells

In mitosis, cohesions are cleaved..

At the end of metaphase

In meiosis, cohesions are cleaved..

Along the chromosome arms in anaphase I (separation of homologs) and at the centromeres in anaphase II (separation of sister chromatids)