y11 bio

• The order of bases in a triplet (three bases) produce long chains of specific amino acids, which code for a protein
• Discontinuous variation: where the characteristics fall into distinct categories
• Continuous variation: where there is a complete range of measurements from one extreme to another
• Meiosis: a type of cell division that makes gametes
• Fertilisation: the fusion of two gametes
• Homologous chromosomes are pairs of chromosomes that carry the same genes, where one chromosome comes from the mother and one from the father
• 1. meiosis is a type of cell division that produces 4 genetically unique gametes with half the number of chromosomes
• 2. Halving the number of chromosomes ensures that when gametes are joined together at fertilisation, the zygote end up with the correct number of chromosomes in each cell to function correctly
• 3. during meiosis, there is independent assortment of homologous chromosomes and independent assortment of chromosomes. This creates a new combination of alleles that are different from their parents. This increases genetic variation
• 4. Fertilisation randomly joins male and female gametes and mixes the genetic information of two parents. This increases genetic variation
• 3 types of mutations: harmful, neutral, beneficial
• Harmful mutations: create proteins that don't function properly
• Beneficial mutations: create proteins that function better than the original
• Neutral mutations: no effect on the protein created
• Mutations are a random and permanent change in the DNA
• Mutations are caused by (1) mutagens: certain chemicals or radiation
• Mutations are caused by (2): and error in the replication of DNA just before a cell divides
• Point mutation: mutations that only change one gene
• 3 types of point mutation: Substitution, Deletion, Insertion
• Substitution (pm): One nucleotide is replaced by another in the DNA sequence
• Deletion (pm): One nucleotide is removed from the DNA sequence, changing many triplets and the reading frame of the sequence
• Insertion (pm): An extra nucleotide is added in the DNA sequence, affecting many triplets in the DNA sequence
• Chromosomal mutation types: Translocation, Inversion, Deletion, Duplication
• Translocation (cm): A piece of chromosome breaks off and attaches to another chromosome.
• Deletion (cm): a part of a chromosome is lost
• Inversion (cm): a segment of a chromosome breaks off, flips around, then reattaches to the chromosome
• Duplication (cm): a part of a chromosome is copied more than once
• Natural selection:

  1. Genetic variation exists
  2. Phenotype better suited
  3. Survive and reproduce, favourable alleles passed down
  4. Frequency of alleles increases, chances of survival of species increases
• Selective breeding: choosing parents with particular characteristics to breed together and produce offspring with more desirable characteristics
• Inbreeding: the production of offspring from the mating or breeding of individuals or organisms that are closely related
• Implications of Inbreeding: inbreeding depression, health impact, reduced genetic diversity
• Punnett squares: the actual outcome does not always match expected outcome. Sample size is small, each fertilisation is independent of all other fertilisations, fertilisation is random
• Test cross with homozygous recessive
• Pure breeding: homozygous for a trait
• DNA sequencing: the process of identifying the exact order of the bases in a DNA strand
• Genetic markers: a gene or DNA with a known location on a chromosome
• Gene: a section of DNA that produces a protein that codes a particular trait
• 4 bases: Adenine pairs/bonds with Thymine, Cytosine pairs/bonds with Guanine
• Base sequence: the order of bases (A, T, C and G) in DNA that form the genetic code.
• The discovery of the structure of DNA in 1953 was made possible by Dr Rosalind Franklin's X-ray diffraction work at King's College London. Her creation of the famous Photo 51 allowed Maurice Wilkins, Francis Crick and James Watson to deduce the double-helix structure of deoxyribonucleic acid