Lesson 8: MEIOSIS AND GENETICS

MITOSIS

process by which a single cell divides into two identical daughter cells. Essential for growth and repair.

MEIOSIS

process by which a single cell divides into four daughter cells, each with half the number of chromosomes of the parent cell. Critical for sexual reproduction (production of gametes).

DIPLOID CELL

cells with two sets of chromosomes.

HAPLOID CELL

known as gametes; contain only one set of chromosomes.

SOMATIC CELLS

cells in the body other than sperm and egg cells.

GAMETES

an organism's reproductive cells (sex cells).

HOMOLOGOUS CHROMOSOMES

one of a pair of chromosomes with the same gene sequence, loci, chromosomal length, and centromere location.

TETRAD

4 sister chromatids of pair homologous chromosomes.

SYNAPSIS

pairing of homologous chromosomes.

CROSSING OVER

recombination of alleles in homologous chromosomes.

GENES

A portion of the DNA that determines a specific trait.

ALLELES

Different forms of the same gene.

CHIASMATA

The point of contact between two non-sister chromatids belonging to homologous chromosomes where crossing over can occur.

MEIOSIS I (Reduction division)

Prophase I: Synapsis and crossing over occur.

MEIOSIS I (Reduction division)

Metaphase I: Tetrads line up at the equatorial plane.

MEIOSIS I (Reduction division)

Anaphase I: Homologous chromosomes separate and move to opposite poles.

MEIOSIS I (Reduction division)

Telophase I & Cytokinesis: Formation of two haploid daughter cells.

INTERKINESIS

short pause before entry into Meiosis II. No DNA replication.

MEIOSIS II (Equational division)

Prophase II: No DNA replication.

MEIOSIS II (Equational division)

Metaphase II: Chromosomes line up at the equator.

MEIOSIS II (Equational division)

Anaphase II: Sister chromatids separate.

MEIOSIS II (Equational division)

Telophase II & Cytokinesis: Results in four haploid daughter cells.