Mutation Part 1 PDF

Topics for 2nd Half Discuss: - Different types of mutation - DNA repairs mechanism - Microbial genetic - Hardy-Weinberg principle - Natural selection and random genetic drift - Population Genetic 1 MUTATIONS  What Are Mutation...

Topics for 2nd Half Discuss: - Different types of mutation - DNA repairs mechanism - Microbial genetic - Hardy-Weinberg principle - Natural selection and random genetic drift - Population Genetic 1 MUTATIONS  What Are Mutations? Changes in the nucleotide sequence of genetic material May occur in somatic cells (aren’t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring  Mutations Mutations happen randomly Almost all mutations are neutral Chemicals & UV radiation cause mutations Many mutations are repaired by enzymes  Are mutations harmful or helpful? Mutation in somatic cell can lead to skin cancers and leukemia Some mutations may improve an organism’s survival (beneficial) Mutation: Phenotypic Effects The effects of mutations on phenotype range from no observable change to lethality.  No observable effect Because of the degeneracy of the genetic code, mutations have no effect on the phenotype of the organism. These are called neutral mutations.  Category of Mutation 1. Chromosomal mutation a. Chromosomal structure (Disjunction) b. Chromosomal numbers (Non-Disjuction) 2. Gene mutation a. Chromosomal structural mutations Inversion, Duplication, Deletion, Insertion, Translocation, Chromosome Mutation Animation Chromosomal number mutation 11  Gene mutation Change in the nucleotide sequence of a gene May happen due to copying errors, chemicals, viruses, etc. Several types of gene mutations involved point mutation (substitution), frameshift, insertion, deletion  Point Mutation (substitution) Change of a single nucleotide Includes the substitution of ONE nucleotide in a gene Changes in the third base of a codon often have no effect. >> Degenerate codon  Point mutation Normal gene Substitution mutation GGT CTC CTC ACG CCA GGT CTT CTC ACG CCA ↓ ↓ CCA GAG GAG UGC GGU CCA GAA GAG UGC GGU Codons ↓ ↓ Pro-Glu-Glu-Cys-Gly Pro-Glu-Glu-Cys-Gly Amino acids  Point Mutations (Substitutions) Normal gene Substitution mutation GGT CTC CTC ACG CCA GGT CAC CTC ACG CCA ↓ ↓ CCA GAG GAG UGC GGU CCA GUG GAG UGC GGU Codons ↓ ↓ Pro-Glu-Glu-Cys-Gly Pro-Arg-Glu-Cys-Gly Amino acids Substitutions will only affect a single codon Their effects may not be serious unless they affect an amino acid that is essential for the structure and function of the protein.  Point mutation Normal gene Substitution mutation GGTCTCCTCACGCCA GGT CTC CTC ACT CCA ↓ ↓ CCA GAG GAG UGC GGU CCA GAA GAG UGA GGU Codons ↓ ↓ Pro-Glu-Glu-Cys-Gly Pro-Glu-Glu-STOP Amino acids  Missense mutation Point Mutation Silent Nonsense mutation mutation 17 Type of mutation? 19  Frameshift Mutation Original: –The fat cat ate the wee rat. Frame Shift (“a” added): – The fat caa tet hew eer at. Amino Acid Sequence Changed  Frameshift Mutation Inserting or deleting one or more nucleotides Changes the “open reading frame” like changing a sentence Production of INCORRECT protein  Mutations: Additions A frame shift mutation Normal gene Addition mutation GGT CTC CTC ACG CCA GGT GCT CCT CAC GCC A ↓ ↓ CCA GAG GAG UGC GGU CCA CGA GGA GUG CGG U Codons ↓ ↓ Pro-Glu-Glu-Cys-Gly Pro-Arg-Gly-Val-Arg Amino acids  Mutations: Deletions A frame shift mutation Normal gene Deletion mutation GGT CTC CTC ACG CCA GGT C/C CTC ACG CCA ↓ ↓ CCA GAGGAGUGCGGU CCA GGG AGU GCG GU Codons ↓ ↓ Pro-Glu-Glu-Cys-Gly Pro-Gly-Ser-Ala- Amino acids Frameshift mutation: Tay sach disease 25 26  Common gene mutations in HUMAN Disorder Mutation Chromosome Color blindness P X Cystic fibrosis F 7q Haemophilia F/P X Sickle-cell disease P 11p Tay–Sachs disease F 15 P – Point mutation, F – frameshift mutation 27 Gene Mutation Animation  Mutation: Spontaneous or Induced Spontaneous mutations occur without a known cause due to inherited metabolic errors or unknown agents in the environment. Induced mutations result from exposure or organisms to mutagens, physical and chemical agents that cause changes in DNA, such as ionizing irradiation, ultraviolet light, or certain chemicals.  Mutation Frequency Spontaneous mutations are infrequent – Bacteria and phage: 10–8 to 10–10 per nucleotide pair per generation – Eukaryotes: 10–7 to 10–9 per nucleotide pair per generation, or 10–4 to 10–7 per gene per generation Treatment of bacteria with mutagens can increase the mutation frequency to > 1% per gene  Conditional Lethal Mutations Conditional lethal mutations are – Lethal in the restrictive condition but – Viable in the permissive condition.  Conditional Lethal Mutations (Favism) Favism is a sex-linked, inherited condition that results from deficiency in enzyme glucose-6- phosphate dehydrogenase Most common among people in Mediterranean, African and Southeast Asian Need to avoid eating fava beans 32  Conditional Lethal Mutants Temperature-sensitive mutants will grow at certain temperature but not at another.