biology topic 2

Chromosome

Chromosome

coils of DNA

23 pairs - 46 TOTAL

Prophase

chromosomes condense

nuclear envelope breaks down=chromosomes free in cytoplasm

metaphase

chromosomes line up down the centre of the cell

Anaphase

cell fibres from each pole of the cell pull chromosomes to opposite poles

Telophase

chromosomes reach opposite poles where they uncoil and become thing again

interphase 1

cell grows and organelles (ribosomes and mitochondria) increase in bumber

DNA is replicate to form an X shape and energy stores are increases

Cytokensis

Two identical daughter cells form when the cytoplasm and cell membrane divide

why multicelluar organisms require continous supply of new cells

Growth

Development

Repair

what can uncontrolled cell division lead to

tumor = cancer

embryonic stem cell

Form when egg and sperm cell fuse to form a zygote

Differntaites into ANY cell

can be used to replace insulin cells for diabetes,neural cells for alzheimers or nerve cells for those paralysed with spinal cord injuries

Adult stem cells

Bone marrow

can form LIMITED amount of cells

Meristems

Roots and shoot tips of PLANTS

differntiate into any plant

can be used to make clones of the plant

Therapeutic cloning

Embryo producing same genes as patient

-can grow into any cell patient needs =tissues/organs

-adv.-has same genetic material as individual

Therapeutic cloning PROS AND CONS

Refelx arc

stimulus detected by receptors→sensory→CNS passes it to relay→motor→effector causes muscle/gland to contract

Synapse

-chemical neurotransmitter is released

-diffuses across synapse

Myelin sheath

allows nerve transmission to travel faster

What has to happen for growth in plants?

cell division,elongation and differentiation

What has to happen for growth in animals?

cell division,differentiation