cell divison

Define the interphase ?

-Long periods of Growth

What happens during the interphase ?

-DNA is replicated

-protein synthesis occurs

-Mitochondria grow and divide ,increasing in number in the cytoplasm

-The normal metabolic process occur

What happens to the animal cell when a cleavage furrow forms ?

• The cell surface membrane is pulled inward by the cytoskeleton until it is close enough to fuse around the middle ,forming two new cells.

What happens during G1 ?

-Organelles replicate

-The cell increases in size

Why can’t plant cells from a cleavage furrow ?

-They have cell walls

What happens during plant cytokinesis ?

• T he vesicles from the Golgi apparatus assemble at the equator to the cell

• The vesicle fuse with each other and the cell membrane ,dividing the cell into two .

• New sections of cel wall form along the new sections of membrane

What happens during stage S ?

-DNA is replicated in the nucleus

Define cytokinesis ?

• The actual division of the cell into two separate cells

What happens during stage G2 ?

-The cell increases in size

-The duplicated DNA is checked for errors

-Energy stores are increased

What are the two stages of the mitotic phase ?

-Mitosis-the nucleus divides

-Cytokinesis-The cytoplasm divides and two cells are produced

What do some cels go into G0 ?

-Differentiation(A cel that becomes specialised)

-The DNA of a cell may be damaged .

As you go older the number of senescent cells increases

Give an example of cells which go into G0 ?

• Nerve cells

• Liver cells

What happens during G1 checkpoint ?

• The checks for :

• Cell size

• Nutrients .

• DNA damage is checked

• If it meets the requirements it enters S if not it enter G0

What are the requirements to pass the G2 checkpoints ?

• check for :

• Cell size

• DNA replication

• DNA damage

Why are checkpoints needed ?

-They monitor and verify whether he proves of each phase of the cell cycle have ben accurately completed for the next stage

What are the requirements to pass the metaphase checkpoint ?

• The chromosomes should be attached to spindles and have aligned

Whats the importance of mitosis important ?

-Growth and repair

-Asexual reproduction

Define centromere ?

-A region where two chromatids join together

Why is the centromere important ?

• It keeps the chromatids together which is necessary for mitosis

• It also the chromatids to be precisely manoeuvred and segregated into the two new daughter cells

What is DNA converted into before mitosis ?

• Into two Chromatids

What are the four stags of mitosis ?

• Prophase

• metaphase

• anaphase

• Telophase

Describe what happens during the prophase stage ?

1.Chromatin begins to coil and condense to form chromosomes .The nucleolus disappears and the nuclear envelope begins to break down

2.microtubules form spindle - shaped statures linking the poles of the cell

3.Two centrioles migrate to the end of the opposite poles of the cell

4.The spindle fibres attach to specific area on the centromere and start to move the chromosomes to the centre of the the cell

5.The nuclear envelope will disappear

Describe what happens during the metaphase ?

• The chromosomes are moved by the spindle fibres to form a metaphase plate

Describe what a happens during the Anaphase?

• The centromeres holding together the pairs of chromatids in each chromosomes divide.

• The chromatids are separated pulled to opposite poles of the cell by shortening spindle fibres

Describe what happens during the Telophase ?

• The chromatids have reached the poles and are now called chromosomes

• The two new sets of chromosomes assemble at each pole and the nuclear envelope reformed around them

• The chromosomes uncoil and the nucleolus is formed

Define metaphase plate ?

• A plane in the centre of the cell

Define a chromatid ?

-A newly copied chromosome