Mutations Hollywood’s images of mutation Mutations Ectrodactyly Severe Combined Immunodeficiency Disorder (SCID) Sickle Cell Anemia Heterochromia iridium Progeria Hypertrichosis What is a mutation? @A mutation is any change in a cell’s [email protected] A mutation can occur in an individual gene - results in a single changed protein - bacterial resistance to antibiotics is an example of a beneficial gene mutation What is a mutation continued A mutation can occur in a chromosome - a chromosome contains many genes - chromosomal mutations affect many proteins Examples: Down Syndrome Edward’s Syndrome Cri-du-Chat What Causes Mutations? Can be caused by mutagens- a physical or chemical cause of mutation. Examples: UV light, radiation, drugs, and benzene. Mutagens are often also carcinogens – anything that causes cancer Can be natural, random events. - mutations occur in 1/100,000 DNA replications Mutations do not have to be bad (evolution) Point Mutations Substitution @A single nucleotide is [email protected] Can change one amino acid in a protein Milk – Mile GGACAATCA GGACCATCA proline -valine-serine proline-glycine-serine Frameshift Mutations @A nucleotide is either inserted or deleted from a [email protected] -all of the triplets from the point of mutation onward will be changed Frameshift Mutations Insertion An insertion occurs when a nucleotide is added to a gene Example: A nucleotide is inserted The fat cat ate the rat The faa tca tat eth era t -the extra nucleotide shifts all of the triplets that follow Frameshift Mutations Deletions A deletion occurs when a nucleotide is removed from a gene. Example: A nucleotide is removed The fat cat ate the rat Thf atc ata tet her at Insertion GGACAATCA proline -valine-serine Deletion GGACAATCA proline -valine-serine GCGACAATCA arginine-cysteine-stop GGAAATCA proline-leucine Chromosomal Mutations Chromosomal mutations involve changes in the number or structure of chromosomes. Chromosomal Mutations Deletion involves the loss of all or part of a chromosome. Chromosomal Mutations Duplication produces an extra copy of all or part of a chromosome. Chromosomal Mutations Inversion reverses the direction of parts of a chromosome. Chromosomal Mutations Translocation occurs when part of one chromosome breaks off and attaches to another. Harmful and Helpful Mutations The effects of mutations on genes vary widely. Some have little or no effect; and some produce beneficial variations. Some negatively disrupt gene function. @However, without mutations, organisms cannot [email protected] Mutations are the source of genetic variability in a species. Harmful Effects Some of the most harmful mutations are those that dramatically change protein structure or gene activity causing genetic disorders. Some cancers, for example, are the product of mutations that cause the uncontrolled growth of cells. http://www.pbs.org/wgbh/nova/cancer/grow_ flash.html Harmful Effects Sickle cell disease is a disorder associated with changes in the shape of red blood cells. Normal red blood cells are round. Sickle cells appear long and pointed. @Sickle cell disease is caused by a point mutation in one of the polypeptides found in [email protected] (the blood’s principal oxygencarrying protein) Beneficial Effects Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments. For example, mutations have helped many insects resist chemical pesticides. Beneficial Effects Plant and animal breeders often make use of “good” mutations. The condition in which an organism has extra sets of chromosomes is called polyploidy.