Cell division

mitosis, meiosis, stem cells

what are the names of the stages of the mitotic cell cycle ?

Interphase, Prophase, metaphase, anaphase, telophase, cytokinesis

what does indapendent assortment mean

when homologous chromosomes are randomly seperated causing genetic variation

what happens during interphase ?

DNA is replicated and checked, proteins synthesised, mitochondria and chloroplast grow and divide

What are the three stages of Interphase

G1- growth

S- synthesis, increase quantity of DNA, enough for two cells

G2- growth

What happens in G0?

Where cells leave the cycle temporarily or permanently. Differentiation, DNA might be damaged

what are Histones ?

Its a protein. DNA wounds around it to from chromatin

what is a chromatin?

make up chromosomes. DNA and Histones make consist of it

what are chromatids?

after chromsomes replicate, there are two identical strands. The strands are chromatids, they are known as sister chromatids

what are the point of checkpoints in the cell cycle for ?

They monitor and verify whether the process at each stage have been accurately completed before the cell is allowed to progress into the next phase

what does the G1 checkpoint check for?

Cell size, nutrients, growth factors and DNA damage

what does the G2 checkpoint check for?

cell size, DNA replication, Mutations

what does the spindle assembly checkpoint check for ?

should be when all the chromosomes should be attached to spindles and have aligned. Mitosis cannot proceed until this checkpoint is passed

why do cells undergo mitosis ?

growth, repair, aesexuall reproduction, differencitation

what is the equation for calculating mitotic index?

cells in mitosis/ total number of cells

what is a centromere?

the area that joins two chromatids together

what are the stages of mitosis called?

prophase, metaphase, anaphase , telophase

what happens during Prophase?

• Nuclear envelope breaks down

• chromosomes condense

• nucleolus disappears (by the end)

• Centrioles migrate to opposite sides of the cells and microtubules start to assemble around centrioles to form the spindle

• chiasma is the crossing point on the homologous pairs

• Homologous chromosomes pair up forming bivalents

what happens during metaphase?

chromosomes line up in the centre of the cell( the equator/metaphase plate)

chromosomes attach to spindle fibres

what happens during anaphase?

centromere divides, separating the chromatids

chromatids are then pulled to opposite sides of the cell as the spindle fibres shorten

what happens during telophase?

chromatids reach the poles of the spindle, called chromosomes now

a nuclear envelope forms around each set of chromosomes

cell division/ cytokinesis begins

what happens during cytokinesis in animal cells?

a Cleavage furrow forms and the plasma membrane is pinched to form two identical daughter cells

what happens during cytokinesis in plant cells?

vesicles from the golgi assemble where the equator was, the vesicles fuse with each other and the membrane. New cell walls are formed.

what are the 8 stages of meiosis?

prophase i, metaphase i, anaphase i , telophase i, prophase ii, metaphase ii, anaphase ii , telophase ii

what is a gamete ?

a sex cell e.g sperm or egg . Contain only half number of chromosomes. They are formed via meiosis. they are haploids

what is a zygote ?

a fertilised egg formed by the fusion of gametes

what are homologous chromosomes?

two pairs of chromosomes, one pair is from the mother (maternal) another pair is from the father (paternal). They have the same gene sequence, but might have different allels

what are alleles?

genes for a particular characteristic. Homologous chromosomes will have the same genes in the same position

what happens during meiosis i ?

• seperation of homologous pairs into two cells

• each cell will only contain one full set of genes, so haploid

what happens during meiosis ii?

pairs of chromatids are separated forming two more cells, 4 haploid cell are produced in total

what happens in prophase i ?

chromosomes condense

nuclear envelope disappears

centrioles move to opposite sides of the cell

nucleolus disappears

homologous chromosomes pair up and cross over can occur

what happens during metaphase 1 ?

same as metaphase in mitosis.

• homologous pairs of chromosomes assemble along equator of cell, independent assortment

• each chromosome of a bivalent attaches to spindle by centromere

what is a bivalent?

when homologous chromosomes pair up

what happens during anaphase 1?

homologous chromosomes are pulled to either side, chromatids stay joined to each other. the results of crossing over are visible and give non identical sister chromatids

what happens at telophase 1?

chromosomes assemble at each pole and the nuclear membrane reforms. Chromosomes decondense, spindle fibres break down

what happens during prophase 2 ?

chromosomes (consisting of 2 chromatids) condense, nuclear envelope breaks down and spindle formation begins

what happens during metaphase 2?

individual chromosomes assemble on the equator. Due to crossing over chromatids are no longer identical so there is independent assortment.

what happens during anaphase 2?

centromeres divide, chromatids are pulled to opposite poles of the cells

what happens during telophase 2?

chromatids reach opposite poles, nuclear envelope forms, chromosomes decondense

results in 4 haploid cells

what are erythrocytes funtions?

transporting oxygen around the body

what adaptations do erythrocytes have ?

• flattened bioconcave shape

• large SA:V

• no nucleus

• haemoglobin

• flexable to fit through capillaries

what are neutrophils functions?

engulf pathagens , play a role in the immune system

what adaptations do neutrophils have ?

• multi lobed nucleus, so can fit through small gaps

• cytoplasm contains lots of lysosomes that contain enzymes which attack pathogens

what adaptations do sperm cells have ?

• flagellum so they can move

• many mitochondria, gives them energy to swim

• head contains digestive enzymes, which allow for it to digest the layer around the ovum

what are sperm cells functions?

to deliver genetic information to the female gamete, the ovum

what are palisade cells functions?

absorbtion of sunlight for photosynthesis

what adaptations do palisade cells have ?

• large amounts of chloroplast

• thin cell walls

• large vacuole maintaining turgor pressure

what adaptations do root hair cells have ?

• have root hair which increase the surface area , maximsing the uptake of minerals in soil

what are root hair cells functions?

uptaking minerals from the soil

what are guard cells functions?

necessary for the movement of gases in and out of the plant

what adaptations do guard cells have ?

• cell wall is thicker on one side, so dosent change shape symmetiraclly with volume

nervous tissue?

support transmission of electrical impulses

connective tissue ?

to hold tissues together or as a transport medium

what are the 4 main categories of tissue in animals?

nervous, epithellial, muscle and connective

what adaptations do squamous epithelial tissue have ?

• very thin

• one cell thick

what are squamous epithelium functions?

diffusison across surfaces. Forms lining of lungs and allows rapid diffusion of oxygen in blood

What are ciliated epithelium functions

Lines trachea, causing mucus to be swept away

What adaptations do ciliated epithelium have

• hair like structures called cilia

• Goblet cells release mucus which traps unwanted particles

What adaptations do cartilage have

• contains fibres of protein

• Firm and flexible

What are the functions of cartilage

Connective tissue, prevents bones from rubbing

What are the functions of muscle tissue

Contract and relax

What are the adaptations of muscle tissue

• shorten in length

• Skeletal muscl fibres contain myofibrils which contain contractible proteins

What are different typer of plant tissue ?

• epidermis tissue, cover plants

• Vascular tissue, transport water and minerals

What are the functions of the epidermis tissue

They allow CO2 in and out, and allow O2 in and out

What are the adaptations of epidermis tissue?

Lots of stomata

What are the functions of xylem tissue ?

Vascular tissue, transport of water and minerals through the cells

What are the adaptations for xylem tissue ?

• vessel elements, which elongate dead cells

• Lignin strengthens th walls of these cells

What are the functions of the phloem tissue

Transport of nutrients around the plant

Phloem tissue apadatations

Columns of sieve tube cells, separated by perforated walls called sieve plates

Name three organ systems

Digestive system

Cardiovascular system

Gaseous exchange system

What does totipotent mean

Stem cell that can differentiate into any type of cell, e.g fertilised egg

What does pluripotent mean ?

Stem cells that can form all tissue types but not whole organisms, present in early embryos

What does multipotent mean

Can only form a range of cells with certain types of tissue. Haemotopeic stem cells

What does unipotent mean

Specialised cell

What are the Sources of animal stem cells

Embryonic stem cells - totipootents

Tissue adult stem cell - multi potent

Sourced of plant stem cells ?

Are present in meristematic tissue (meristem )

What are the uses of stem cells

• drug trails

• Alzheimers

• Parkinsons disease

• Type 1 Diabetes

• Development of biology

What are the ethics surrounding stem cells

• can result in the destruction of embryos

• Religious and ethic

• Can pass on diseases

• Infection risk

• Ignore rights of embryo

Reasons for stem cells

• spare embryos would have been destroyed anyway

• Organs for transplant are in short supply

• You can’t undiscover something