Principles of Genetic Variation

• Nucleotide: The smallest unit of DNA
• A base goes with T bases
• G bases goes with C bases
• Karyotypes are an arrangement that shows all of an organisms chromosomes parts in order.
• Genes are short sections of DNA that codes for a specific protein
• Alleles: Different variants of the same gene.
• Proteins are long chains of amino acids folded into a specific shape
• The base sequence of the DNA can be broken down into triplets (three-base sequence) to code for a amino acid
• Triplets carry the code for specific amino acids
• Proteins have important structural roles as well as many chemical reaction roles
• Different amino acids lead to different proteins led to different phenotypes
• There are 23 different chromosomes in the human body
• Genomes are the entire base sequence of the indivuals DNA
• The bonds between bases are called hydrogen bonds, they are weak
• Continous variation: where there is a complete range of measurements from one extreme to another e.g height, body mass
• Discontinuous variation: where the charactertics fall into discrete categories e.g. attached/unattached ear lobes, tongue roller/ non tongue roller
• Sexual reproduction involves the combination of DNA from two genetically different organisms - through the fusion of gametes. The offspring is also genetically different of the two parents
• Siblings are genetically differnt
• Genetic variation is the differences in DNA of the base sequence in individuals
• There is a higher chance for survival if species are genetically diverse - this means if there is environment change some species will be able to adapt and survive.
• There are 20 different amino acids
• Monomers means building blocks of something e.g. nucleotides are building blocks of DNA
• Mutations are random, permanent changes in the base sequence of DNA
• Somatic cells are body cells
• Point mutation is when one (or a few) base at on place in a gene are changed
• Substitution mutation is when on base is replaced with a different base in a gene - least likely to have significant impact on the organisms survival
• Deletion mutation is when base(s) are removed from a gene (possibly) causing a frame shift to occur.
• Insertion is when base(s) are added to a gene, causing a frame shift to occur.
• Reasons why mutation would occur

  1. Error ins DNA replication (gametes, fertilisation)
  2. External influences (Mutagens) e.g. radiation, sunlight, smoking, etc
• Mutation is the source of new genetic variation, new alleles
• Point mutation is the umbrella term for the three different types of mutation n
• Frameshifts cause the biggest impact if a mutation can impact the change in survival of an individual/species
• Chromosomal mutation affect the whole chromosomes, meaning they can affect many genes and have severe implications.
• Trisomy are 3 copies of chromosomes in one position by nondisjunction. .
• Monosomy is having only one copy of chromosomes instead of two caused by nondisjunction
• Down syndrome is the cause of trisomy 21 by nondisjunction
• Klinefelter syndrome: a condition in which a person is born with an extra X chromosome (being a male but having less male sex charactersitcs and some female characteristics)
• Turner Syndrome: A genetic disorder in which a female is born with only one X chromosome. (monosomy)
• Homologous pairs are two chromosomes of the same length with the same genes - they both have some genes but different alleles
• Meiosis is the type of cell division produced by gametes