Mutations 1

Mutations Change in any part of DNA/Changes in the nucleotide sequence of DNA May occur in somatic cells (not passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring 2

Mutations Mutations can occur in any cell. They only affect future generations if they occur in the cells that produce the gametes: these are “germinal” or “germ line” mutations. Mutations in other cells are rarely noticed, except in the case of cancer, where the mutated cell proliferates uncontrollably. Mutations in cells other than germ line cells are “somatic” mutations.

Mutations A human body contains 1013 - 1014 cells approximately. The average mutation rate for any given nucleotide is about 1 in 109. That is, on the average 1 cell in 109 has that particular nucleotide altered. This means that virtually every possible base change mutation occurs repeatedly in our body cells.

What Causes Mutations? There are two ways in which DNA can become mutated: Mutations can be inherited. Parent to child Mutations can be acquired. Environmental damage

Significance of Mutations Most are neutral Eye color Birth marks Some are harmful Sickle Cell Anemia Down Syndrome Some are beneficial Sickle Cell Anemia to Malaria Immunity to HIV

Are Mutations Helpful or Harmful? Mutations happen regularly Almost all mutations are neutral Chemicals & UV radiation cause mutations Many mutations are repaired by enzymes 7

Are Mutations Helpful or Harmful? Some type of skin cancers and leukemia result from somatic mutations Some mutations may improve an organism’s survival (beneficial) 8

Types of Mutations Chromosome Mutations Gene mutation

Chromosome Mutations May Involve: Changing the structure of a chromosome The loss or gain of part of a chromosome 10

Chromosome Mutations Five types exist: Deletion Inversion Translocation Non disjunction Duplication 11

Deletion Due to breakage A piece of a chromosome is lost 12

Inversion Chromosome segment breaks off Segment flips around backwards Segment reattaches 13

Duplication Occurs when a gene sequence is repeated 14

Translocation Involves two chromosomes that aren’t homologous Part of one chromosome is transferred to another chromosomes 15

Translocation 16

Non disjunction Failure of chromosomes to separate during meiosis Causes gamete to have too many or too few chromosomes 17

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Chromosome Mutations Down Syndrome: Chromosome 21 does not separate correctly. They have 47 chromosomes in stead of 46. Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of intelligence.

Chromosome Mutations Cri-du-chat: Deletion of material on 5th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps

Chromosome Mutation Animation 21

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Gene Mutations Change in the nucleotide sequence of a gene May only involve a single nucleotide May be due to copying errors, chemicals, viruses, etc. 23

Types of Gene Mutations Include: Point Mutations Substitutions Insertions Deletions Frame shift 24

Point Mutation Change of a single nucleotide Includes the deletion, insertion, or substitution of ONE nucleotide in a gene 25

Point Mutation Sickle Cell disease is the result of one nucleotide substitution Occurs in the hemoglobin gene 26

Frame shift Mutation Inserting or deleting one or more nucleotides Changes the “reading frame” like changing a sentence Proteins built incorrectly 27

Frame shift Mutation Original: The fat cat ate the wee rat. Frame Shift (“a” added): The fat caate the wee rat. 28

Amino Acid Sequence Changed 29

Gene Mutation Animation 30