The cell cycle - a series of events from the time a cell forms until its cytoplasm
- includes all phases (interphase) and mitosis
- all single cells of multicellular organisms go through the cell cycle
- cells multiply through division
Interphase - the interval between mitotic division when a cell grows
- a typical cell spends most of its life in this phase
- a cell doubles the number of its cytoplasmic components and replicates its DNA
- 3 stages of interphase
— G1: metabolic activities - cell growth and everything is doubled but DNA
— S: DNA Synthesis - DNA is doubled
— G2: protein synthesis needed for cell division - checkpoints to see if a cell is ready for mitosis
Mitosis - the process of nuclear division that maintains chromosome number
- every cell does this but sperm and egg cells
- when a cell divides by mitosis, it produces two descendant cells
- Mechanism of gene expression control determine whether or not a cell divides
- There are four stages of Mitosis: Prophase, Metaphase, Anaphase and Telophase/Cytokinesis
Prophase - the first stage of cell division where the chromosomes become paired chromatids and the nuclear envelope disappears
- one of two centrosomes move to the opposite end of the cell
- microtubules assemble and lengthen forming spindles
- sister chromatids are attached to opposite centrosomes
Metaphase - the second stage of cell division where chromosomes attach to the spindle fibers
Anaphase - the stage of cell division where the chromosomes move away from one another to opposite poles of the spindle
- near the end of this phase, cytokinesis or the actual cytoplasmic cell division may occur in most eukaryotes
—cytokinesis differs among plant and animal cells
Telophase - the final phase of cell division where the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed
- near the end of this phase, cytokinesis or the actual cytoplasmic cell divison may occur in most eukaryotes
Telomeres - a region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with nearby chromosomes
- in other words, it's function is to contain the chromosome to itself
- They are non coding repeat DNA sequences
- telomere buffers are important
Mutations - some mutations can affect the cell cycle
- can cause loss of gene function and their protein products
- controls that limit gene expression may fail
—when enough checkpoint mechanism fail, a cell loses control over its cell cycle
—neoplasm - accumulation of abnormally dividing cells
Cancer - disease where abnormal cells divide uncontrollably and destroy body tissue - a malignant neoplasms that gets progressively worse and is dangerous to health
- there is no known cure, there are only methods of controlling and containing it.
— Such as chemotherapy
- Causes 15-20% of deaths in developing countries
- mutations in checkpoint genes are required to make a normal cell into a malignant one
—lifestyle can reduce the risk of requiring these mutations
- some neoplasm can be detected beforehand with periodic screenings