BABS1201 Lecture Notes - Lecture 14: Genetic Variation, Cleavage Furrow, Sister Chromatids

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BABS1201 Notes LEC 14
LEC 14: Mitosis and Meiosis
Cell cycle:
o Interphase growth and replication of cellular components
o Mitotic phase cells separate into two daughter cells
MITOSIS:
G2 of interphase DNA is replicated in the nucleus
Prophase chromatid starts to condense into chromosomes and early mitotic
spindles form
Prometaphase nuclear envelope starts to be broken down, fibres from the
centrosomes are attaching the centromeres of the chromosomes and where they
attach is the kinetochore.
Metaphase chromosomes line up along the centre of the cell due to equal
pressure from being pulled by fibres to opposite ends, centromeres are anchored to
the plasma membrane, and chromosomes have to be attached by both ends before
proceeding to anaphase.
Anaphase there is a protein that holds the sister chromatids together, a specific
protease (protein enzyme) digests this protein to allow the chromatids to separate
to opposite ends of the cell
Telophase chromosomes starts to de-condense and the nuclear membrane begins
to reform
Cytokinesis Cleavage furrow starts to form and the daughter cells separate into
two separate cells (animal cell)
o Vesicles containing cell wall material travel between the two daughter cells
to form a cell plate that the cell wall fuses with to separate and form two
daughter cells
Checkpoints:
o G1 waits for a signal indicating for the cell to divide, and ensures all
materials have been required for DNA synthesis
o G2 checks the DNA that has been replicated is correct and intact
o M just before anaphase, checking that every chromosome is attached on
both sides and lined up in the centre correctly
Apoptosis genetically programmed cell death:
o Removes unwanted and damaged cells allowing their contents to be used
and recycled (e.g. leaves providing protective layer during winter then used
as nutrients during spring when decaying.)
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