D2.1 Mitosis*

All organisms need to produce new cells for

growth maintenance and reproduction

cell divition

A parent cell will divide to produce daughter cells

prokaryotes through

binary fission

eukaryotes through

mitosis - create somatic cells

meiosis - create gamates

cytokinesis

division of cytoplasm

cytokinesis in animals cells

Actin and myosin proteins form a contractile ring

Pinches the cell membrane together

Forms a cleavage furrow

Deepens and split the cytoplasm in two

cytokinesis in plant cells

Vesicles containing cell wall materials fuse to form a cell plate

Cell plate grows outwards until it reaches the existing cell wall

Fuses with existing cell wall to split the parent cell into two daughter cells

vesicle

phospholipid bilayer vacuole - use to transport substances

cellulose stored inside

division of cytoplasm is usually

equal

both daughter cells must what for cytokinesis

receive a mitochondrion and any other organelle that can only be made by dividing a pre-existing structure

ensure the same structure and the same function

unequal cytokinesis example

budding in yeast and oogenesis in humans

budding in yeast

Reproduce asexually through budding

Nucleus divides by mitosis

Small outgrowth (bud) on mother cell is formed

Receives one of the nuclei but only a small share of cytoplasm

Dividing wall constructed separating the two cells leaving a budding scar

Oogenesis in humans

Process of producing mature egg cells in humans

Begins with two divisions of a mother cell

First division produces one large cell with nearly all the cytoplasm and a small polar body

Large cell goes on to carry out the second division - unequal division again to form one large cell and one small polar body which does not develop further

what must occur before mitosis or meiosis

dna repllication

when does dna replication occur

interphase

After replication, each chromosome consists of

two genetically identical sister chromotids held tgt by a centromere

before nucelar division what happens

chromatin supercoils into condensed sturcture to enable efficient seperation of dna

chromatin

loosely packe dna with histones

four phases of mitosis

prophase metaphase anaphase telophase

prophase

• DNA supercoil: chromatin condenses and becomes sister chromatids, which are visible

under the light microscope.

• Nuclear membrane is broken down and disappears

• Centrosomes move to the opposite poles of the cell and spindle fibres begin to form

metaphase

• Spindle fibres (microtubules) from each of the centrosomes attach to the centromere of sister chromatids.

• Chromatids line up in the equator.

anaphase

• Contraction of the spindle fibres cause the separation of the sister chromatids

• The chromatids are now considered as chromosomes.

• Chromosomes move to opposite poles of the cell.

telophase

• Chromosomes uncoil to become chromatin

• Spindle fibres break down and new nuclear membrane reform at opposite pole

cell elongates and prepares for cytokinesis

mitosis are diploid or haploid

diploid

interphase

prepration stage before mitosis and meiosis

containing g1 s g2

- G1 Phase:

obtain more nutrients—increase cytoplasm volume increase in cell size

s phrase

dna replication/synthesis

g2 phase

double the amount of organelle and protein synthesis

increase transcription and translation as well (cell size also increases).

any translation or transcription during mitosis?

no because dna supercoil

mutagens types

biological mutagens - viruses

chemical - cigarettes

physical - UV light

Protooncogenes

regulates the cell cycle - if mutagen - cause this gene to mutate - becomes oncogenes - leading to uncontrolled division

primary tumor

- Oncogenes / mutagen / Tumor suppressor gene

Secondary tumor -

migration of cancer cells (metastasis)

when transcription and translation occur

g2

movement of chromosomes include what 2 structures

microtubules and microtubule motors

Microtubule motors

Specialised proteins that bind to microtubules and hydrolyse ATP

Provide energy to move chromosomes to either pole of the cell

Microtubules

Long, thin, cylindrical fibrous proteins that form the spindle apparatus during cell division

Responsible for pulling chromosomes apart during division

before nuclear division, what chromatin does

supercoils into condensed structures to enable efficient separation of replicated DNA

mitosis is haploid or diploid

diploid

mitosis somatic cells or gametes

somatic cells

mitotic index

measure of the proliferation status of a cell population

if mitotic index too high

cancer

if mitotic index too low

low repair rate

photos of 4 stages

calculate mitotic index

cells in mitosis/total number of cells