Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Revision Notes 1
...

• Before it occurs, DNA is replicated in Interphase
...

• There are 4 phases to it: prophase, metaphase, anaphase, and telophase
...

Interphase consists of 3 phases: G1, S, and G2
...

In the S phase the chromosomes are replicated
...

• Because the DNA molecules are very long, they have to be condensed and the DNA coils to
become shorter and wider
...

Phases of mitosis
Prophase
• Chromosomes become shorter and fatter by coiling, and successively, supercoiling
...

• Microtubules grow from MTOC to form a spindle-shaped array that links the poles of the cell
...

Metaphase
• Microtubules continue to grow and attach to the centrosomes in each chromosome
...

• The microtubules shorten and the attachment is put under tension to test if it’s done correctly
...

Anaphase
• Each centromere divides, allowing the chromatids to separate from each other
...

• Mitosis produces 2 genetically identical nuclei because sister chromatids are pulled to opposite
poles
...

• They are pulled in a tight group near the MTOC and a nuclear membrane forms around them
...

• By now the cell is already dividing
...


• In animal cells the plasma membrane is pulled inwards to form a cleavage furrow
...

• These proteins are actin and myosin and are similar to the ones that cause contraction in
muscles
...

• In plant cells vesicles are moved to the equator where they fuse and form tubular structures
across it
...

• They connect to the existing plasma membrane, and the division is completed
...

• Cyclins bind to enzymes called cyclin-dependent kinases, which become active and attach
phosphate groups to other proteins in the cell
...

• There are 4 types of cyclins in a human cell
...


Tumour formation and cancer
• Tumours are abnormal groups of cells that develop at any stage of life in any part of the body
...

• Diseases due to this are known as cancer
...

• All mutagens are carcinogenic
...

• Mutations are random changes to the base sequence of a gene
...

• Oncogenes are normally involved in the control of the cell cycle, this is why mutations in them
can result in an uncontrolled cell division and therefore tumour formation
...

• However, because the cells in our body are a lot, the chances are greater in a life-time
...

• Metastasis is the movement of cells from a primary tumour to set up secondary tumours in the
body

---