Cell Cycle

Cell Divison

* important biological process from the continuity of life
* on other cell → identical daughter cells, identical genetic material needs to be split between the two daughter cells except during meiosis

genome

complete genetic material of an organism or virus

cell divison: prokaryotes

a single circular chromosome

cell divison: eukaryotes

multiple linear compact chromosomes

Genetic Material

* genome consists of all the genetic information that determines organisms heritable traits

gene

discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA

Nucleosome

basic unit of chromatin, the DNA is would twice around a protein core composed of two copies of each of four types of histones

1 centromere

region on each sister chromatid where sister chromatids attach to each other by proteins binding to specific DNA sequences

2 chromatids

identical copies of the same original chromosome joined all along their lengths by protein complexes cohesins, that are cleaved during their separation

large diversity in genomes

* genome size the number of chromosomes and the number of genes vary tremendously between species
* many species genomes have been duplicated over their

Mitosis

nuclear division in eukaryotic cells division into five stages


1. prophase
2. prometaphase
3. metaphase
4. anaphase
5. telophase

G2 of interphase

* presence of the nuclear envelope and one or more nucleoli
* centrosome duplication into 2 centrosomes that organize the spindle microtubules
* chromosomes duplicated during S phase are not condensed

prophase

* chromatin fibers become more tightly coiled, condensing into discrete chromosomes
* nucleoli disappear'
* centrosomes move away from each other

prometaphase

* nuclear envelope fragments
* microtubules extending from each centrosome can now invade the nuclear area
* chromosomes have become even more condensed
* microtubules not attached to the kinetochores interact with the microtubules from the opposite pole of the spindle

metaphase

* centrosomes are at opposite poles of the cell
* chromosomes have reached the metaphase plate

anaphase

* cohesins that binds sister chromatids are cleared by a separate protein
* two sister chromatids of each chromosome pair separate each chromatid now becomes a distinct chromosome
* liberated daughter chromosomes move toward opposite ends of the cells as their kinetochore microtubules shorten

telophase

* two daughter nuclei form in the cell. nuclear envelopes arise from fragments of the parent cell nuclear envelope and other portions of the endomembrane system
* nucleoli reappear
* chromosomes become less condensed
* division of one nucleus into genetically identical nuclei

Cytokinesis

* division of the cytoplasm is initiated during the late telophase and involves the cytoplasm

Binary Fission in Prokaryotes

* prokaryotes do not undergo mitosis but instead divide by binary fission
* cell division is initiated when the DNA of the bacterial chromosome begins to replicate at the origin of replication producing two origins