Mutations

1. Mutations Types of Mutations | Effects of Mutations

2. Learning Objectives • Identify different changes to DNA within both genes and chromosomes • Evaluate effects of changes to DNA on proteins produced and organisms’ overall survival • Mutations

3. Gene mutation – a mutation that only affects one gene • Insertion – an event in which one or more nucleotides are added within a DNA sequence for a gene • Deletion – an event in which one or more nucleotides are removed from a DNA sequence for a gene • Substitution (point mutation) – an event in which a nucleotide is replaced with a different nucleotide • Gene Mutations

4. Types of mutations can be determined by Step 1Write the wild-type allele above the mutated allele so that the bases line up. Step 2 Starting on the right, look along both strands and underline the first base that is different in the mutated allele. Step 3 Based on the difference between the two strands, identify the mutation that occurred. Step 4 If possible, use the overall lengths of the two strands to check your answer. • Gene Mutations

5. Step 1 Write the wild-type allele above the mutated allele so that the bases line up. Step 2 Starting on the right, look along both strands and underline the first base that is different in the mutated allele. Step 3 Based on the difference between the two strands, identify the mutation that occurred. Step 4If possible, use the overall lengths of the two strands to check your answer. Does the result make sense? • Gene Mutations Example Ex) Which of the three gene mutations occurred to change the sequence ACTAGATAGGCAT to ACTAGATAGCAGCAT? Wild-type ACTAGATAGGCAT Mutated ACTAGATAGCAGCAT Wild-type ACTAGATAGGCAT Mutated ACTAGATAGCAGCAT An insertion occurred. Longer mutated strands reflect an insertion. Yes.

6. Chromosomal mutation – a mutation that affects multiple genes • Chromosomal deletion – an event in which a piece of the chromosome is deleted • Can remove one or more genes from chromosome • Chromosomal Mutations

7. Chromosomal mutation – a mutation that affects multiple genes • Amplification – an event in which a large piece of the chromosome is repeated • Causes two or more copies of one or more genes • Chromosomal Mutations

8. Chromosomal mutation – a mutation that affects multiple genes • Inversion – an event in which one or more new nucleotides removed and flipped before being reinserted • Reverses orientation • Chromosomal Mutations

9. Segments of DNA can also move from chromosome to chromosome • Chromosomal insertion – an event in which a piece of the chromosome is removed and inserted into a different chromosome • Translocation – an event in which two pieces of different chromosomes are interchanged • Chromosomal Mutations

10. Some mutations happen during meiosis • Homologous chromosomes are separated • Each one goes into a different gamete • Non-disjunction – an event in which the homologous chromosomes do not separate and instead both go to the same daughter cell • Chromosomal Mutations

11. Mutations categorized by • Change to nucleotides • Effect on the polypeptide made • Each type of change to nucleotide  certain type of effect of polypeptide • Effects of Mutations

12. Substitution mutations can affect genes in multiple ways • Different codon does not always change amino acid used • Silent mutation – a mutation in which there is no effect on the polypeptide chain created • No outwardly visible affect • Effects of Gene Mutations

13. Substitution mutations can affect genes in multiple ways • Different codon does not always change amino acid used • Missense mutation – a mutation that results in the insertion of a different amino acid • Amino acids now different • Can change proteins created • Effects of Gene Mutations

14. Substitution mutations can affect genes in multiple ways • Different codon does not always change amino acid used • Nonsense mutation – a mutation in which a stop codon is expressed early, creating a shorter polypeptide chain • Greatly affects protein created • Effects of Gene Mutations

15. Genetic code has many redundancies, which can cause silent mutations • Effects of Gene Mutations

16. Insertions and deletions cause frameshift mutations • Frameshift mutation– a mutation in which the codon reading frame is altered, potentially changing all codons following • Codons are read in groups of three nucleotides • Addition or removal of a nucleotide changes the reading frame • Different polypeptides produced • Effects of Gene Mutations

17. Chromosomal mutations affect multiple genes • Have large impact on organism • Non-disjunction • Creates one gamete with extra copy and one with no information • If either fuses with normal gamete, individual formed has abnormal number of chromosomes • Down syndrome – a human genetic disorder caused by having an extra chromosome #21 • Physical and mental retardation • Effects of Chromosomal Mutations

18. Overexpression– the creation of more protein than normal from a gene • Creates more copies of protein than normal • If chromosome is deleted or inversed, organism might not be able to express any of the genes • Effects of Chromosomal Mutations

19. Mutations categorized by effect on fitness • Beneficial mutations – a mutation that increases an organism’s fitness • Fur color may allow organism to better blend into the environment, avoiding predators • Harmful mutation– a mutation that decreases an organism’s fitness • May make protein used to carry oxygen less efficient • Neutral mutation– a mutation that does not affect an organism’s fitness • No change in proteins • All silent mutations are neutral mutations • Effects of Mutations

20. Learning Objectives • Identify different changes to DNA within both genes and chromosomes • Evaluate effects of changes to DNA on proteins produced and organisms’ overall survival • Mutations