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