Mitosis and Meiosis

meiosis

type of cell division that results in 4 daughter cells that each have half the number of chromosomes as the parent cell.

Diploid

A cell containing two full sets of chromosomes 2n=46.

Haploid

A cell containing a single/ half set of chromosomes n=23

Gametes

A haploid male or female germ cell (e.g. sperm and egg) produced via meiosis

gene

a section of the DNA (chromosome) that codes for a specific trait (e.g. eye color or hair color)

crossing over

when homologous chromosomes exchange genes during Prophase 1 creating new mixture of parent traits in their offspring

Meiosis I

PMAT I: The first cell division of meiosis when the homologous pairs are split up into two separate cells.

Meiosis II

PMAT II: The second cell division of meiosis. This is when the sister chromatids are split up into two separate cells.

Mitosis

Produces cells almost genetically identical

46 pairs of chromosomes

How many pairs of chromosomes present in humans

Chromosome

Coiled up DNA

Chromatin

Uncoiled DNA. Present in interphase

Somatic

Body cells (liver, skin, etc), The type of cells that undergo mitosis

Homologous Chromosomes

Chromosomes of the same size and length that carry the same type of information (gene for hair color), one from mom and one from dad

Function and location of Mitosis

Cell division for growth, repair or maintenance. Occurs in somatic cells.

PMAT

Function and location of Meiosis

Cell division for gamete production (sperm and eggs). Happens in gonads (ovaries and testes).

PMATPMAT

Phases of the Cell Cycle

1. Interphase (G1, S, G2)

2. Mitosis (PMAT)

3. Cytokinesis (cell division)

Events in Prophase

Chromatin coils up into chromosomes.

Centrioles move to poles.

Spindle fibres and asters form. Nucleus and nucleolus

disappear.

Events in Metaphase

Chromosomes line up at the metaphase plate.

MIDDLE

Cytokinesis

Cell divides into two. Cell plate forms in plant cells.

Cancer cells

Cells that keep reproducing. Can move and grow in another part of the body - metastasis. Don't specialize

Sexual Reproduction

Requires male and female gametes. Variation.

Asexual Reproduction

One parent only. (cloning)

Mitosis.

Parthenogenesis in reptiles.

Crossing over

Homologous chromosomes may exchange genetic material during prophase I.

Occurs more often in genes that are further apart.

Interphase I

G1 - growth, protein synthesis

S - DNA replicates

G2 - growth, protein synthesis

Prophase I

Synapsis - homologous chromosomes (tetrads) pair up.

Crossing over may occur - exchange of genetic material.

Metaphase I

Homologous pairs line up in the middle on the metaphase plate.

Anaphase I

Segregation - Homologous pairs separate to opposite poles.

Telophase I

Cleavage furrow. Replicated chromosomes reach the poles.

Prophase II

Chromosomes can be seen.

Cells are haploid (n).

Metaphase II

Chromosomes line up in the middle

Anaphase II

Centromeres split. Single chromosomes move apart.

Telophase II

Cleavage furrow.

Fertilization

When a sperm enters an egg. It doubles the chromosome number.

Ex. In humans:

Sperm (23) + egg (23) = zygote (46 chromosomes) OR n + n = 2n

Zygote

sperm + egg or fertilized egg

2n

Sources of variation

1. Gamete success

2. Crossing over

3. Independent Assortment

Independent Assortment

The way the homologous pairs line up in Metaphase I is RANDOM!

tetrad

structure containing four chromatids that forms during meiosis to allow for crossing over to occur

Centrioles

Cell organelle that aids in cell division in animal cells only

Centromere

Region of a chromosome where the two sister chromatids attach

spindle fibers

Protein structures which move the chromosomes during cell division.

Chromatid

one half of a duplicated chromosome

sister chromatids

Identical copies of a chromosome; full sets of these are created during the S subphase of interphase.

Purpose of interphase

Growth, DNA replication, and organelle duplication

S phase of Interphase

chromosome replicate and DNA synthesizes

G1 Phase of Interphase

Longest phase, cell grows, organelles duplicate, RNA synthesizes and enzymes

G2 phase of Interphase

More RNA and protein synthesis, ATP storage in prepartion fo rmitosis

Prophase of Mitosis

Metaphase of Mitosis

Anaphase of Mitosis

Telophase of Mitosis