BIOL 1411 1st Edition Lecture 28Outline of Last Lecture I. Developmental Genetics & MutationsOutline of Current Lecture II. MutationsLectureMutations- Changes at the level of DNA sequenceo point mutation- results from the gain, loss, or substitution of a single basepair of DNAo Small indels- insertions or deletions of a few to hundreds of basepairs of DNAo Chromosomal mutations- more extensive- may change the position of genes or cause multiple genes in a DNA segment to be duplicated or lost- Mutation: change in DNA sequenceo DNA is a stable repository for genetic information. Semiconservative replication maintains an old copy of each base sequence in each newly replicated moleculeo But changes in DNA sequence occur, both spontaneously and through external factors - What are mutations?o Spontaneous mutations- several mechanisms that can change DNA: Bases can have differentstructures- may form tautomers; a rare tautomer can pair with the wrong base Chemical reactions may change baseso Induced mutation- caused by mutagens: Chemicals can alter bases Some chemicals add other groups to bases. DNA polymerase will then add any base there. o Radiation damages DNA: Ionizing radiation such a X rays creates free radicals- highly reactive- can change bases and break sugar phosphate bonds UV radiation is absorbed by thymine, causing it to form covalent bonds with adjacent nucleotides- disrupts DNA replication o Measuring the mutation rateThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Haploid Human Genome – 3,000,000,000 bp- 35 new mutations inherited from each parent; 70 total in each person born- 130 million births each year, so on average each position in the human genome have >1 new variant produced annually o Cost and Benefits of Mutations Costs- Some germ line and somatic cell mutations are harmful or lethal, leading to genetic diseases and cancer- Mutations commonly responsible for recessive mendelian traits occurred long ago, exist as genetic load Benefits- Provide the raw material for evolution in the form of genetic diversity- Evolution would not be possible without mutation- Inherited PKU in humanso Genetic mutations may make proteins dysfunctionalo Phenylketonuria (PKU) results from an abnormal anzyme phenylalanine hydroylase- normallycatalyzes conversion of dietary phenylalanine to tyrosineo The common PKU allele produces an abnormal enzyme with tryptophan instead of arginine at position
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