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Genetics - Coggle Diagram
Genetics
Variation
Alleles
Genes have two different forms called alleles, e.g one for tall one for small
Each offspring mist inherit one allele from each parent - homozygous - both chromosomes have same allele - heterozygous is different
Dominant - only needs one allele to be present to be expressed
Recessive - needs two alleles to be present
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Genetic crosses
Punnet square - place parents alleles along sides of square and work out probability. - uppercase = dom lower = rec
genotypes - allele combination
phenotypes - what they look like
Codominance
Some alleles do not show perfect dominant recessive relationship
3 phenotypes - combination of 2 is the 3rd - displayed with uppercase then exponent with other letter, e.g red and white genotype is pink phenotype - both expressed
Genetic variation - following sexual reproduction, organisms will have different version of genes to a different individuals
Environmental variation - environment affects the characteristics of an organism - adapts to surroundings
Continuous - smooth range of measurements, Discontinuous - distinct catogories
Mutations
Stem cells
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Adult stem cells - only differentiate into a few different types of cell - used to treat many diseases
Natural selection
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MVARPS - mutation, variation, advantage, reproduce, pass on allele, several generations
Antibiotic resistance
Bacteria becoming resistant to many antibiotics due to natural selection - as they reproduce very quickly and can take advantage of mutation
due to overuse of antibiotics
Mutation is a change in the sequence of bases in DNA - rare events - caused by ionizing radiations and chemicals such as tobacco - increases genetic variation
Genes
DNA
Deoxyribonucleic acid stores genetic information and controls cell activities - instructions to build proteins
Double helix shape, sugar phosphate backbone, Adenine, cytosine, guanine and thymine - A with t, C with G
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Protein synthesis
Transcription
two stands of DNA helix are unzipped via the enzyme helicase - weak hydrogen bonds between base pairs
The enzyme polymerase attaches to DNA - moves along DNA strand - U pairs with A, G pairs with C
leaves nucleus and travels to ribosome
Translation
mRNA passes through ribosome, for every codon it lines up to a complementary anticodon on the tRNA
tRNA molecules hold specific amino acids and lines up according to gene codons
Chain of several hundred form polypeptide
then folded into correct shape to form protein