Gene Mutations An Introduction to Genetic Mutations: Mutations that arise during translation may not be too big of an issue since it only likely made that mistake once If mutations that arise during transcription may also not be too big of an issue since the transcript is only used a couple times Mutations are most likely to occur at the level of the DNA Can be inherited (pass down from parents to offspring) or can also occur spontaneously (where a person suddenly gets a mutation in their DNA without getting it passed down from their parents) Two Different Types of Mutations: Point Mutations: when one DNA nucleotide is mutated to a different one Missense Mutations: when the point mutation cause a change in amino acid (can leave out a huge chunk of DNA) Conservative Mutation: when the new amino acid is of the same type as the original (glutamate → aspartate) Non-conservative Mutation: when the new amino acid is of a different type than the original (glutamate → valine) Silent Mutation: since multiple codons code for the same amino acid, then you could essentially change a nucleotide without changing the amino-acid sequence Frameshift Mutation: when a single nucleotide is added/deleted from the sequence and ends up pushing the reading frame over (messing with the entire sequence that follows) Nonsense Mutation: introducing a premature stop codon to the DNA sequence The Causes of Genetic Mutations: Causes of point mutations: base substitution (transition is a swap between A/G or C/T, transversion is a swap between A/T or G/C) A mispair is when A pairs with anything other than T, and same with the other bases (more common for it to still be an interaction between a pyrimidine and a purine The causes of a frameshift mutation is either through an insertion or deletion Large scale mutations occur at the chromosomal level and can affect many genes at one time Translocation: when a gene from one chromosome is swapped for a gene on another chromosome (between nonhomologous chromosomes) Chromosomal Inversion: when two genes on the same chromosome switch places and affect how the gene is regulated in addition to what the genes actually code for Mutagens & Carcinogens: Mutagen: any chemical/physical substance/event that causes genetic mutations (such as poisons or sun exposure) Endogenous: comes from within and is some mutagen already found within the organism The most common form is reactive oxygen species (naturally occurring in the human body from metabolism produced from mitochondria during oxidative phosphorylation such as superoxide or hydrogen peroxide) and can often lead to the double strand break (breaks DNA’s double helix into 2 smaller pieces) or base modification (when the nucleic acid bases are changed/swapped around) Exogenous: comes from outside the organism/external environment Ethidium Bromide (EtBr) which jumps into a DNA double helix and stick itself between the two strands and can seriously deform the structure of the DNA, causing some serious problems Base Analogs: pretend to be a certain base but then end up acting differently than that base ever would Oxidative Stress: occurs when ROS levels are increased and can be counteracted with antioxidants Carcinogen: can be mutagens but not all of them are, can be thought of as something that can lead to cancer (uncontrollable cell proliferation) Examples include tobacco, asbestos, and UV radiation The Effects of Mutations: Mutations can vary greatly with regards to them being “good” or “bad”, in fact most probably go unnoticed in the human body Sickle cell disease causes much less efficiency with regards to circulating oxygen around the human body (bad) but also gives a person an increased resistance to malaria since the parasite can’t grow as good in the sickle cells (good)