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B2 (3) (Genes, alleles and DNA (Alleles and DNA fingerprinting (Most genes…
B2 (3)
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Mendel
Experiments
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He decided
- Each plant must have two 'factors' for flower colour
- The purple factors were 'stronger' than the white factors
- Each factor must be separately inherited, that is, the factor did not 'blend' together
When he presented his experiment s in 1865 no one knew about cell divisions or chromosomes. This meant his theory was only rediscovered after 1900
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How genes work
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Mutations
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Many people have slightly different version of the haemoglobin. It differs by only one base in the DNA but it is enough to cause a serious condition called sickle cell anaemia
In condtions where oxygen is in short supply, it makes the red blood cells go so badly out of shape that they clump together and get stuck in blood capillaries
Genetic Disorders
Inherited
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Pterodactyl(more than 5 fingers or toes) is caused by the dominant allele so in order to have it it must come from the dominanant
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Embryo screening
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This involves testing the embryos' DNA to find out if any have the alleles, then only implanting the unaffected ones into the mother's uterus
Fossils
Record
Fossils provide evidnce which suggests that all species of living things that exist today have evolved from simple life-forms
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Evolution
Animals having common ancestors is very likely as all living things contain a genetic code in their DNA
Extinction
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Mass
Sudden, catastrophic event which produced mass extinction and changes
New Species
How
1-Geographical Isolation, 2- Genetic Variation, 3-Natural Selection, 4-Speciation
Isolation
Any situation that forces members of the same species to start breeding within selected groups can cause a new species to arise
