Biology Mieosis

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

What type of cell division happens most of the time?

mitosis

When does meiosis happen?

sexual reproduction

Goal of meiosis

For 1 diploid cell to become 4 haploid cells

Number of rounds in meiosis

2

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

Crossing over

Different forms of a gene

Alleles

How must the alleles be in crossing over?

aligned

Result of crossing over

genetic diversity and 4 different chromosomes

Production of mature egg characterized by an unequal cytokinesis

Oogenisis

Phases of Meiosis 1

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

Phases of Meiosis 2

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

Prophase 1

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

Metaphase 1

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

Anaphase 1

Spindle fibers pull homologous chromosomes to opposite sides of the cells

Telophase 1 and Cytokinesis

Nuclear membrane forms. Spindle disassembles. The cell splits into two cells with 23 chromosomes and 46 chromatids

Prophase 2

2 haploid daughter cells with 23 chromosomes each are introduced from Meiosis 1. New spindle fibers are created.

Metaphase 2

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

Anaphase 2

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

Telophase 2 and Cytokinesis

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

fertilized egg

Zygote

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

Tetrad

Variable for diploids

2n

Variable 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 chromosomes

Set of chromosomes in which part comes from the female parent and part from the male parent. A pair of chromosomes that may each have the same genes in the same order, but with a variation between them.

Interphase

Happens once before Meiosis 1. Cell growth, DNA replication and cell functions occur.