cell division - mitosis

what are the functions of cell division

growth, repair of tissues and organs, maintenance to replace dead or dying tissues

how long does the cell cycle take for animal cells

about 12-24 hours

what are the functions of cell division

growth, repair of tissues and organs, maintenance to replace dead or dying tissues

how long does the cell cycle take for animal cells

about 12-24 hours

how many chromatids make up each chromosome

two

what is supercoiling

coiling DNA molecules to make the chromosomes shorter and wider
- histones associate with the DNA to help

what are the stages of interphase

G1, S, G2

G1 Phase

growth - increases the amount of cytoplasm and organelles

S Phase

DNA replication - ensures that new cells have equal amounts of DNA

G2 Phase

growth - organelles for division and mitochondria are formed

Interphase

DNA exists as chromatin
Nucleolus is surrounded by a nuclear envelope
In G2, centrioles are duplicated

what is mitosis

Cell division that generates new cells for growth and repair.

results of mitosis

two daughter cells are identical to mother cell
ensures that all body cells will have a complete number and form of chromosomes

2n=

46

prophase

chromatin supercoils into chromosomes
- two chromosome are called sister chromatids and the chromosomes are joined at the centromere
nuclear membrane breaks down
centrioles move to opposite poles of the cell and sprout microtubules

metaphase

microtubules attach to the centromere (kinetochore proteins) and guide the chromosomes to the metaphase plate (centre of the cell)

anaphase

sister chromatids are separated and pulled to opposite poles by microtubules - separated sister chromatids are now referred to as chromosomes - each pole has a complete set

telophase

chromosomes reach opposite ends of the cell
chromosomes start to unwind and become chromatin
microtubules break down
nuclear membrane forms

cytokinesis

the cytoplasm of a cell is divided between two daughter cells
can begin as soon as chromosomes have separated and are far enough
all cytoplasm and its contents of the mother cell are shared between the two daughter cells

what does oogenesis produce

four haploid cells - 3 out of 4 are used to produce a zygote

how does the unequal cytokinesis help the zygote

provides it with the resources that are needed to survive until it is implanted in the walls of the uterus

cytokinesis in animal cells

a ring of contractile proteins, actin and myosin, pinch inwards around the equator of the cell
- forms a cleavage furrow

cytokinesis in plant cells

• microtubules are built into a scaffold straddling the equators, which is used to assemble a layer of vesicles

• vesicles move to the equator where they fuse to form tubular membranes

• merge to form two layers of membrane across the whole equator which develops in to the membranes of new daughter cells

when is pectin brought

brought in vesicles and deposited by exocytosis between two between the two membranes

how is cellulose deposited

by exocytosis to form the cell wall

what are tumors

abnormal groups of cells

Benign Tumors

Cells 'stick' to each other and do not invade nearby tissues or move to other parts

Malignant Tumors

Cells become detached and move elsewhere in the body and develop into secondary tumors

what are carcinogens

cancer causing chemicals

examples of carcinogens

Viruses, mutagens, X-rays, UV radiation

what are mutagens

gents that cause gene mutations and mutations can cause cancer

oncogenes

genes that become cancer causing after mutating
- involved in the control of the cell cycle and cell division

when a tumor cell has been formed...

it divides repeatedly
- called q primary tumor

metastasis

the movement of cells from a primary tumor to set up secondary tumors in other parts of the body

positive correlation between

smoking and the death rate due to cancer

how many chemicals in cigarettes cause tumors in the lung

20

how many chemicals in cigarette smoke are carcinogenic

40