Meiosis

Gametes are

Gametes are

haploid

Somatic cells are

diploid

somatic cells

body cells

Number of chromosomes in diploids

46

Number of chromosomes in haploids

23

Diploid cells contain

Two sets of homologous chromosomes

Haploid cells contain

One set of chromosomes and half the genes from each parent cell

Homologous chromosomes

set of cells which comes from male and female parent cells

What type of cell division happens most of the time?

mitosis

When does meiosis happen?

sexual reproduction

Number of rounds (meiosis)

2

Goal of meiosis

For 1 diploid cell to become 4 haploid cells

Crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Alleles

Different forms of a gene

How must the alleles be in crossing over?

aligned

Result of crossing over

genetic diversity and 4 different chromosomes

Oogenisis

Production of mature egg characterized by an unequal cytokinesis

Phases of Meiosis 1

Interphase, Prophase 1, Metaphase 1, Anaphase 1, Telophase 1, Cytokinesis

Phases of Meiosis 2

prophase 2, metaphase 2, anaphase 2, telophase 2, cytokinesis

What happens in Prophase 1

Duplicated chromatin forms into sister chromatids. Tetrads form and crossing over occurs. Spindle fibers are created.

What happens in Metaphase 1

Chromosome pairs line up in the center. Spindle fibers attach themselves to the chromosomes.

What happens in Anaphase 1?

Spindle fibers pull homologous chromosomes to opposite sides of the cells

What happens in Telophase 1 and Cytokinesis?

Nuclear membrane forms. Spindle disassembles. The cell splits into two cells with 46 chromosomes

What happens in Prophase 2?

2 haploid daughter cells with 46 chromosomes each are introduced from Meiosis 1. New spindle fibers are created.

What happens in Metaphase 2?

Chromosomes line up in the middle of the cell. Spindle fibers attach to centromeres.

What happens in Anaphase 2?

Sister chromatids are pulled apart and move to opposite sides of the cell.

What happens in Telophase 2 and Cytokinesis?

Spindle fibers disassemble. Two cells each split and 4 haploid cells are made with 23 chromosomes.

Zygote

fertilized egg

Tetrad

Homologous pair of chromosomes each made up of 2 chromatids. Required for crossing over

Variable(s) for diploids

2n

Variable(s) for haploids

n

Polar bodies

The 3 additional haploid cells that will not be fertilized and were created during the creation of an oocyte

Oogenesis

the production, growth, and maturation of an egg, or ovum

Spermatogenesis

production of sperm

synapsis

the process of pairing homologous chromosomes

fertilization

when a sperm and egg combine

homologous

matching chromosomes

What happens in interphase

the cell’s chromosomes duplicate