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Chapter 14 Section 1

Chapter 14 Section 1. Mutations. Are mutations good or bad?. Both!!. Some mutations lead to genetic disorders Some mutations may cause a beneficial trait Some mutations are silent no effect good or bad. What is a Mutation?.

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Chapter 14 Section 1

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  1. Chapter 14 Section 1 Mutations

  2. Are mutations good or bad? Both!! • Some mutations lead to genetic disorders • Some mutations may cause a beneficial trait • Some mutations are silent • no effect good or bad.

  3. What is a Mutation? • Mutation – a change in the structure or amount of the genetic material in an organism • A change in the DNA • A mutant is an individual whose DNA or chromosomes are different.

  4. What causes mutations? • When DNA replicates, mutations occur accidently. • DNA polymerase and other enzymes catch some mistakes, but not all • Very rare • Mutagens – substances that cause DNA to mutate • Examples: radiation, UV light, chemical toxins

  5. What are the effects of mutations? • Mutations may help, harm, or have no effect. • Depends on where the mutation occurs. • Depends on how much DNA is affected

  6. Types of Mutations Gene Mutations • Affect one gene Chromosome mutations • Affect many genes

  7. Point Mutations • Point Mutation – a change of a single nucleotide

  8. Silent Mutation • Silent Mutation – a mutation that has no effect on a gene’s function • Why is this possible? • Because the genetic code is so repetitive

  9. Missense Mutation • Missense Mutation – a mutation that causes the codon to code for a different amino acid • AKA – replacement mutation

  10. Nonsense Mutation • Nonsense mutation – a mutation that causes a codon to change to a STOP codon • Causes protein synthesis to stop early. • Protein may not function

  11. Frameshift Mutation • Frameshift Mutation – a mutation that causes a shift in the reading frame. • Reading frame – the sequence of codons from start to finish

  12. Frameshift Mutation • Insertion – adding one or more nucleotides • Deletion – removing one or more nucleotides • What happens to the reading frame if 3 nucleotides are inserted or deleted?

  13. Chromosomal Mutations • Can occur during meiosis (crossing over) • Usually the homologous chromosomes exchange equally • Sometimes…they do not

  14. Chromosomal Mutations • Deletion – a piece of the chromosome is lost • Usually harmful X-rays

  15. Chromosomal Mutations • Duplication – both pieces remain attached to the same homologous chromosome X-rays

  16. Chromosomal Mutations • Inversion – a piece attaches in the opposite direction X-rays ABCDEFGHIJKLMNOP ABCDEFGHIJKLMNOP ABCDEFGHIJKLMNOP

  17. Chromosomal Mutations • Translocation – a piece ends up on a completely different chromosome X-rays

  18. Chromosomal Mutations • Gene Rearrangement – an entire gene is moved to another location X-rays

  19. Nondisjunction • Nondisjunction – occurs when homologous chromosomes fail to separate • One cell ends up with extra chromosomes • Down syndrome – extra 21 chromosome • Aka – trisomy 21

  20. Are mutations heritable? • Mutations are only inherited if the mutation occurs in the gamete (sperm and egg). • If a mutation occurs in one of your skin cell, it can affect you, but not your children.

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