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Mutations

Mutations. Biology B/Transcription and Translation. Introduction to Mutations. DNA replication is a VERY effective and accurate process; however, there are times when “mistakes” are made.

andrew-gillespie
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Mutations

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  1. Mutations Biology B/Transcription and Translation

  2. Introduction to Mutations • DNA replication is a VERY effective and accurate process; however, there are times when “mistakes” are made. • These “mistakes” can have both positive and negative effects, so we might think of them as CHANGES rather than mistakes. • Mutations are changes in the DNA sequence that affect genetic information.

  3. Types of Mutations • There are two main types of mutations: • Gene Mutations = changes to a single gene • Chromosomal mutations = changes to an entire chromosome (which contains many genes).

  4. Gene Mutations • Some gene mutations involve many nucleotides, but most involve just one. • Point Mutations = changes that affect only one nucleotide. • Example: “Normal” DNADNA with Substitution DNA: TAC GCA TGG AAT DNA: TAC GTA TGG AAT mRNA: AUG CGU ACC UUA mRNA: AUG CAU ACC UUA AA: Met-Arg-Thr-Leu AA:Met-His-Thr-Leu

  5. Gene Mutations • When a point mutation involves inserting or deleting a nucleotide, it has a large effect. • Inserting or deleting a nucleotide affects codon groupings all the way down the DNA strand • Example: “Normal” DNADNA with Insertion DNA: TAC GCA TGG AAT DNA: TAT CGC ATG GAA T mRNA: AUG CGU ACC UUA mRNA: AUA GCG UAC CUU A AA: Met-Arg-Thr-Leu AA: Ile-Ala-Tyr-Leu

  6. Gene Mutations • Frameshift mutations = Insertion or deletion mutations, which affect every amino acid following the insertion or deletion. • Frameshift mutations can alter a protein so much that it is unable to perform its normal functions.

  7. Chromosomal Mutations • Deletion = Loss of all or part of a chromosome. • Duplication= Segment of chromosome is repeated. • Inversion = Part of the chromosome is reversed. • Translocation = Part of one chromosome breaks off and attaches to another chromosome

  8. Chromosomal Mutations

  9. Now it’s your turn… • Remember when we talked about Down Syndrome? • Down syndrome is a developmental disorder caused by an extra copy of chromosome 21 (which is why the disorder is also called "trisomy 21"). • Do you think Down Syndrome is the result of a gene mutation or a chromosomal mutation?

  10. Now it’s your turn… • Remember when we talked about cystic fibrosis? • Cystic fibrosis is a genetic disorder that affects the respiratory and digestive systems. People with cystic fibrosis inherit a defective gene on chromosome 7. • Do you think Cystic Fibrosis is the result of a gene mutation or a chromosomal mutation?

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