2.24c - mitosis 3

- nucleus breaks down - prophase
- chromosomes become visable as 'pair of chromotids'
- protein molecules (spindle, spindle fibre) extend
- chromotids will move to the centre of the spindle
- metaphase - chromotids is attached to the spindle fibre by the centrimere - chromotids are in the middle
- anaphase - fibre shortens splitting the chromotids apart and halves the centrimere
- telophase - formation of 2 nuclei, opposite ends of the cell
- cytokinesis - cell splits into 2

3.24b - mitosis 2

- DNA replication - copying chromosomes
- held together by centralimere - 'pair of chromotids'
- interphase of cell cycle - DNA replication

3.24a - mitosis 1

- mitosis- cell division - growth
- diploid (number of chromosomes in nucleus)
- it will divide into 2
- each have a diploid nucleus which is identical
- indentical because: 1. same number of chromosomes 2. same set of chromosomes

3.16 DNA and genetic information

- sugar phosphate backbone
- in the middle has 4 bases: adenine, thymine, cytosine and guanine
- held together by A-T, C-G (the base pairs)
- the order of bases is always the same (ATGC)
- this all constructs protein for the cytoplasm

3.15 genes

- a gene is a section of a molecule of DNA
- a gene for every charateristic
- gene turns into protein
- protein controls the charateristic

3.14 chromosomes

- choromosomes - genetic information
- the DNA forms a shape called "the double helix"
- 1000's of genes in a chromosome
- genes produces a protein which produces a characteristic e.g blood
- different species have different numbers of chromosomes, humans have 46
- they work in homologous pairs
- same gene located in the same place in each homologus pair

3.1 sexual and asexual reproduction

- sexual reproduction
- two different genders (male/female)
- gametes - sperm (male) egg (female)
- fertilisation - fuse together
- broad differences - not identical

- asexual reproduction
- no sexes, gametes or fertilisation
- clones

why aren't all living things either sexual or asexual in reproduction?