Mitosis and Meiosis
Used for normal cell growth
- Parent cell
- Chromosomes make identical copies of themselves
- They line up along the centre
- They move apart
- Two daughter cells from each with 46 identical chromosomes to the parent cell.
Used to make the sex cells (gametes)
- the chromosomes are copied
- Cells divide twice to give four cells
Sexual and Asexual reproduction
Variation is introduced by:
- Set of genetic info from two parents
- The gametes are produced by meiosis (each gamete is different)
- Some inherited characteristics may be more dominant than others e.g: eye colour, brown and blue.
Asexual: example: a spider plant.
- One parent
- Offspring produced by mitosis
- Genetically identical to the parent
- Are a clone of the parent
- There is NO variation!
Genetics, DNA and Chromosomes
Nucleus->Chromosome->Gene->DNA double helix->Bases
46 Chromosomes to fertilised egg, 23 from each parent.
- Male= x,y the male determines the sex of the baby
- Female= x,x
If there is an extra chromosome= downs-syndrome.
DNA is a double helix
The order of bases A, T, C, G determine our features
- A=Adenine A always pairs with T A sequence of 3 bases codes for
- T=Thymine one amino acid. The sequence of
- C=Cytosine C always pairs with G amino acids determine the protein
- G=Guanine structure and characteristics.
Constant internal environment.
Temperature in the Thermoregulation system
- hair lies flat
- blood vessels dilate-sweat
- flush-capillaries close to skin
- goosebumps-hair traps air
- no sweat
- shivering-generates heat
- blood vessels constrict.
Animal and Plant Cells
Both Animal and Plant cells:
- nucleus-controls cell functions (brain)
- cell membrane-controls entry of chemicals into cell
- cytoplasm-where chemical reactions happen
- endoplasmic reticulum-makes proteins like enzymes
- cell wall-supports cell (protection)
- chloroplasts-site of photosynthesis (chlorophyll)
- vacuole-contains sap and starch granules