Components of Eukaryotic Cells

Plasma Membrane

Nucleus

Cytoplasm

Endoplasmic Reticulum

Golgi Appartus

Ribosomes

Number of Chromosomes

Diploid (2 copies of each organism)

Haploid (cells contain 1 set of chromosomes)

Cellular Reproduction: Interphase

period of growth and development between cell divisions

G1 (gap 1)

Cell grows and proteins are synthesized

G0 (non-divinding phase)

Stable state where cells usually maintain a constant size

S checkpoint

Holds the cell in G1 until the cell has all enzymes and proteins necessary for DNA replication

S phase

chromosomes are duplicate (results in 2 sister chromatids)

G2 (gap 2)

growth and biochemical events

M checkpoint

DNA must be replicated entirely and undamaged

Homologous pair

• 1 chromatid from the sire and one from the dam
• generally similar size and structure
• alleles at same location

Mitosis

Chromosomes separate, and the cell undergoes division

results in a complete set of genetic information for each cell

separated into 6 continuous stages

Interphase

(first step of mitosis) The nuclear membrane is present and chromosomes are relaxed

Prophase

(second step of mitosis) chromosomes condense. Each chromosome posses two chromatids.

The mitosis spindle forms

Prometaphase

(third step of mitosis) The nuclear membrane disintegrates.

Spindle microtubules attach to chromatids

Metaphase

(fourth step of mitosis)

• attached to spindle microtubules
• spindle assembly checkpoint
• chromosomes line up on the metaphase plate

Anaphase

(fifth step of mitosis)

• connection between chromatids break down
• chromatids pulled to opposite poles

Telophase

(sixth step of mitosis)

2 separate nuclei form

Cytokinesis

(6/7 step of mitosis)

• division of cytoplasm
• simultaneous with telophase

Meiosis

Two cell divisions

half number of chromosomes

produces genetic variation amongst sex cells

crossing over

Meiosis 1

Middle prophase 1 (chromosomes begin to condense)

Late prophase 1 (homologous chromosome pair; crossing over takes place and nuclear membrane breaks down)

Metaphase 1 (homologous pairs of chromosomes line up along the metaphase plate)

Anaphase 1 (homologous chromosomes separate and move toward opposite poles)

Telophase 1 (chromosomes arrive at the spindle poles and the cytoplasm divides)

Meiosis II

Prophase II (chromosomes recondense)

Metaphase II (individual chromosomes line up on the equatorial plate)

Anaphase II (sister chromatids separate and move toward opposite poles)

Telophase II (chromosomes arrive at the spindle poles and the cytoplasm divides)

four daughter cells

Medels law of segregation

in the formation of a germ cell or gamete, the two genes at a locus in the parent cell are separated, only one gene being incorporated into each germ cell

Mendels Law on Independent assortment

Genes assort independently during meiosis if all possible gametes are formed into equal proportions