2.5 Cell Division
The eukaryotic cell cycle
Mitosis: Division of the nucleus
Interphase: (90%) Has three subphases called G1, S and G2
G1: (Transcription- translation or protein synthesis) Cellis preparing for S phase, each chromosome is a single
S: DNA replication, there are now two sister chromatids
G2: The cell makes preparation for mitosis
Chromatin: DNA and Histone ] Nucleosome
Two“legs”: Sister chromatids
Is the division of a eukaryotic nucleus into two genetically identical nuclei.
The four phases of mitosis are:
The chromatin coils and supercoils, become more and more compact, condensing into visible chromosomes. The chromosomes consist of identical, paired sister chromatids.
The nucleus envelopebreaks down. Kinetochore microtubes appear and connect the metochores to the poles.
Spindle microtubes attach to the centromeres. Chromosomes are moved to the equator of the cell.Anaphase:
Chromatids separate and the spindle microtubes pull them towards the poles of the cell.
Daughter chromosomes reach the poles. As telophase concludes, the nuclear envelops and nucleolireform, chromatin becomes diffuse, and the cell again enters interphase.
* Is the division of the cytoplasm
Certain agents can damage these regulatory elements. Examples of such agents include: ultraviolet light, chemicals called “carcinogens” or viruses. When this happens , uncontrolled celldivision can occur resulting in the formation of tumor.
These transitions from G1 to S and from G2 to M depend on the activations of a type of protein called cyclin-dependent kinaseor cdk is enzyme that catalyzes the transfer of a phosphate group from ATP to another molecule, this phosphate transfer is called phosphorylation.
* 2.5.6 Mitosis involve:...
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