Inheritance

DNA

Chromosomes found in the nucleus of cells
Chromosomes are long lengths of coiled DNA
Small sections of DNA are called genes which code for proteins
Proteins control processes in the body they also determine inherited characteristics
Different versions of the same gene are called alleles
DNA is a double helix, it has a sugar phosphate backbone
It has four bases A(adenine), T(thymine), C(cytosine), G(guanine)
A pairs with T
G pairs with C -this is complimentary base pairing
Bases are held together with hydrogen bonds
DNA is a type of nucleic acid

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Type of asexual reproduction
New cells made are genetically identical to the parent cells
Cells are diploid- Cells have pairs of chromosomes (46)
Stage 1-The Chromosomes duplicate and the nuclear membrane breaks down
Stage 2-The Chromosomes line up along the centre of the cell
Stage 3-Spindle fibres (cell fibres) pull the chromosomes to opposite ends
Stage 4-Membrane form around the chromosomes to form nuclei
Stage 5-The Cytoplasm divides
Stage 6-Two newdaughter cells are produced
Mitosis in needed for growth of plants and animals and repair of worn out or damaged tissue

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Sexual Reproduction-leads to genetic variation
Happens in the gametes (sperm and egg)
Gametes are Haploid-only has single chromosomes (23)
At fertilisation gametes fuse to form a zygote with a full set of chromosomes (46)
Stage 1-Chromosomes duplicate and nuclear membrane breaks down
Stage 2-Chromosomes line up along the centre, crossing over of chromosomes happens (exchanging sections of chromosomes) and chromosomes get pulled apart to each end of the cell
Stage 3-The Cytoplasm divides
Stage 4-The Chromosomes line up again and are pulled apart to each end of the cell
Stage 5-The Cytoplasm splits
Stage 6-The Nuclear membrane forms and 4 new cells are formed and these are haploid

All four cells are genetically different to eachother

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