Chapter 12-4 DNA Mutations Notes

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1 Chapter 12-4 DNA Mutations Notes

2 I. Mutations Introduction A. Definition: Changes in the DNA sequence that affect genetic information

3 B. Mutagen= physical or chemical agent that interacts with DNA to cause mutations 1. Examples: UV radiation, chemicals

4 C. 2 categories of mutations 1. Gene Mutation (Point Mutation): mutation limited to one or two nucleotides in a single gene 2. Chromosomal Mutation: change in a portion of the whole chromosome. a. Can affect more than one gene

5 II. Gene Mutations- A. 3 Kinds of gene (Point) mutations-changes in one or a few nucleotides in a single gene 1. Substitutions-one base is replaced by another base

6 a. May not change the amino acid i. Why? Multiple codons specify the same amino acid (redundancy of the genetic code)

8 Example: DNA: TAC GCA TGG AAT mrna: AUG CGU ACC UUA A.A.: Met Arg Thr Leu Mutation 1: TAC GCG TGG AAT mrna: AUG CGC ACC UUA A.A: Met Arg Thr Leu Same amino acid sequence-does not affect protein function

11 DNA: TAC GCA TGG AAT mrna: AUG CGU ACC UUA A.A.: Met Arg Thr Leu Mutation 2: TAC TCA TGG AAT mrna: AUG AGU ACC UUA A.A.: Met Ser Thr Leu Different amino acid sequence-may or may not affect protein function

13 2. Insertions-a base is added (inserted) into a gene a. See Figure 12-20

14 Insertion

15 3. Deletions-a base is removed (deleted) from the gene b. See Figure 12-20

17 4. Frameshift Mutations-shift in the reading frame of the genetic message. 1. Insertions and Deletions are examples of frameshift mutations

18 2. See Figure a. ex: THE CAT ATE THE RAT delete "C" THE ATA TET HER AT-

21 Point Mutation Video Clip

22 A mutation that affects every amino acid following an insertion or deletion is called a(an) 1. frameshift mutation. 2. point mutation. 3. chromosomal mutation. 4. inversion. 0% 0% 0% 0% Answer Now frameshift mutation. point mutation. chromosomal mutation. inversion. 20

23 b. The order of amino acids changes depending on where you start reading. c. If the 1 st G is deleted the bottom sequence of amino acids will result & this is a completely different protein!! (Changes the reading frame of the genetic message)

24 The type of point mutation that usually affects only a single amino acid is called 1. a deletion. 2. a frameshift mutation. 3. an insertion. 4. a substitution. 0% 0% 0% 0% Answer Now a deletion. a frameshift mutation. an insertion. a substitution. 20

26 B. Summary: Types of Gene Mutations 1. Base pair substitution 2. Base pair insertion = Frameshift mutation 3. Base pair deletion = Frameshift mutation

28 III. Chromosomal Mutations-changes in the number or structure of chromosomes A. Deletions, Duplications, Inversions, and Translocations

31 Deletion & Duplication Video Clip

34 Translocation & Inversion Video Clip

35 When two different chromosomes exchange some of their material, the mutation is called a(an) 1. inversion. 2. deletion. 3. substitution. 4. translocation. 0% 0% 0% 0% Answer Now inversion. deletion. substitution. translocation. 20

37 A mutation in which a segment of a chromosome is repeated is called a(an) 1. deletion. 2. inversion. 3. duplication. 4. point mutation. 0% 0% 0% 0% Answer Now deletion. inversion. duplication. point mutation. 20

38 A mutation in which all or part of a chromosome is lost is called a(an) 1. duplication. 2. deletion. 3. inversion. 4. point mutation. 0% 0% 0% 0% Answer Now duplication. deletion. inversion. point mutation. 20

39 1. May change the locations of genes on chromosome 2. May change the number of copies of some genes

40 IV. Significance of Mutations A. Most mutations are neutral-they do not disrupt protein function B. Some mutations can lead to cancer or disease

change shape, not work properly, and sometimes cause

42 1. Changing just one amino acid-even if the protein is thousands of amino acids long can cause the protein to change shape, not work properly, and sometimes cause diseases such as sickle cell, cystic fibrosis, and muscular dystrophy.

44 C. Some mutations can be passed on to offspring; only if the mutation is in the germline (sex cells)- we will discuss later in another chapter.

Mutations. Any change in DNA sequence is called a mutation.

Mutations. Any change in DNA sequence is called a mutation. Mutations Mutations Any change in DNA sequence is called a mutation. Mutations can be caused by errors in replication, transcription, cell division, or by external agents. Mutations Mutations can be harmful.