How fast do you think DNA Polymerase can add nitrogen bases (A, T, G, or C) during DNA Replication (in base pairs per minute)? DNA Polymerase can replicate DNA at a rate of 50,000 base pairs per minute! That’s pretty fast – do you think it ever makes mistakes? Mutations Mutations • Changes in the genetic code • They come from mistakes that cells have made in copying their own DNA. – If a cell has a mutation, all of its daughter cells will inherit the same mutation! How many cells have the mutation? A. B. C. D. 1 6 7 8 7! Types of Mutations • Gene Mutation: produces a change in a single gene • Chromosomal Mutations: produce changes in whole chromosomes & affect many genes – Can change the locations of genes on chromosomes! Gene Mutations • Point Mutation: involve changes in 1 or a few nucleotides at 1 point in the DNA sequence – Substitutions – Frameshift Mutations THE DOG BIT THE CAT Point Mutation THE DOG BIT THE CAR Point Mutations – Substitutions • 1 base is changed into another – Usually affect only 1 amino acid Point Mutations – Substitutions Point Mutations – Frameshift Mutations • Insertions or Deletions: an extra base is added or removed – These usually affect a large part of the protein! Remember! Bases are read in groups of 3, but if 1 base is added or removed, this shifts the “reading frame” of the genetic code & can change all amino acids after the site of the mutation! Deletion The original: THE DOG BIT THE CAT Deletion: THE DOG BIT HEC AT Insertion The original: THE DOG BIT THE CAT Insertion: THE DOE GBI TTH ECA T Point Mutations – Frameshift Mutations Chromosomal Mutations - Inversion • Reverses the direction of parts of the chromosomes Chromosomal Mutations - Translocation • Part of 1 chromosome breaks off & attaches to another Chromosomal Mutations – Deletions & Duplications • Deletion: part of the chromosome is lost • Duplication: there is an extra copy of part of the chromosome What type of chromosome mutation does Brenden have? A. B. C. D. Inversion Translocation Deletion Duplication Inversion! Effects of Mutations • An amino acid may or may not change! – For example, the codons GCC & GCA both code for the same amino acid, alanine! – However, mutating AGC to AGA will change the amino acid from serine to arginine! All mutations are harmful. A. True B. False False! Effects of Mutations • Any new trait in a population, good or bad, is a result of a mutation! • Neutral: no effect on protein function • Harmful: cause genetic diseases • Beneficial: gives the organism a better chance of survival Examples • Neutral: Blue eyes was caused by a mutation that first appeared 6-10 thousand years ago! • Harmful: An albino person has a frameshift mutation in melanin producing genes. Albinism makes organisms more susceptible to skin cancer. • Beneficial: Mutations in the CCR5 gene in humans makes them almost immune to HIV! Which type of mutations are more likely to be harmful? A. B. C. D. E. Substitutions Insertions Deletions A&C B&C Insertions & Deletions! These mutations will always cause a frameshift mutation, which will change the reading frame & the amino acid sequence! This will give you a completely different protein! Substitutions could change the amino acid sequence, but it may not. Exit Ticket – Before you leave, answer the following question on a sheet of paper (share!): The majority of plants & animals are able to make their own Vitamin C. Some animals, including humans, guinea pigs, & some birds, have lost their ability to make Vitamin C due to a mutation. Would you consider this mutation to be harmful, neutral, or beneficial? Why?