MUTATIONS Biology 12 JOKE OF THE DAY WHAT
MUTATIONS Biology 12
JOKE OF THE DAY:
WHAT ARE MUTATIONS? � Changes in the nucleotide sequence of DNA � May occur in somatic cells (aren’t passed to offspring) � May occur in gametes (eggs & sperm) and be passed to offspring � The errors may occur during transcription to m. RNA sequence or during DNA replication
CAUSES: � Exposure to mutagenic agents can increase the chance of mutations occurring � UV (ultraviolet) radiation � Chemicals � X rays
TYPES OF MUTATIONS � Chromosomal � Affects multiple genes � May affect genes on separate chromosomes � Point Mutation (gene mutation) � Copying errors � Only one or a few nucleotides are affected
TYPES OF POINT MUTATIONS: 1. 2. 3. Deletion Insertion Substitution
1. DELETION �A nucleotide is left out � This shifts the reading of the DNA over one resulting in an incorrect protein AAG CCC GGC AAA AA CCC GGC AAA ← shifts over Result: AAC CCG GCA AA
1. DELETION CONT’D m. RNA Protein Met Lys Phe Gly Ala Nucleotide deletion Met Lys Leu Ala His
2. INSERTION � An extra nucleotide is added � This shifts the reading of the DNA over one resulting in an incorrect protein AAG CCC GGC AAA AAG ACC CGG CAA A
2. INSERTION CONT’D
FRAME SHIFT: � Inserting or deleting one or more nucleotides changes the “reading frame” like changing a sentence � Proteins built incorrectly � Silly example: � Original: �The fat cat ate the wee rat. � Frame Shift (“a” added): � The fat caa tet hew eer at.
3. SUBSTITUTION � One nucleotide replaces another and creates a new codon � Only affects one amino acid in the protein � Possibly could be a silent mutation AAG CCC GGC AAA AAG ACC GGC AAA
3. SUBSTITUTION CONT’D m. RNA Protein Met Lys Phe Gly Ala Lys Phe Ser Ala Base substitution Met
SILENT MUTATION � Amino DNA CTA = CTG = acid is not changed RNA Amino Acid GAU = Asp GAC = Asp
TRY IT : � m. RNA 1. 2. Translate the m. RNA above into amino acids. Translate each mutated m. RNA below. A. B. C. 3. 4. = GCU ACU CAA UUC GCU ACU CGA UUC GCU ACG CAA UUC GCU ACU UCA AUU C What was the result of each mutation? Which would be most harmful?
TRY IT : � Page 263 � Questions: � Page 2, 6, 7 274 � Questions: 10 (a, b)
- Slides: 16