Definition : Any change in the nucleotide sequence of DNA

What Causes It? 1. Changes in the environment OR mutagens (other sources of mutation are physical and chemical agents) a. Ultraviolet Light (UV) b. X-Rays c. Tar from tobacco d. Pollutants and chemicals 2. Errors during replication, transcription or translation

Chromosomal vs. Gene  Chromosomal Mutations: take place when the number of chromosomes changes or when structural changes occur in the chromosomes  Gene Mutations: a permanent change in the DNA sequence that makes up a gene

Types of Gene Mutations  Point o Substitution  Frameshift o Deletion o Insertion

Point Mutations A point mutation is when a single base pair is altered.

Substitution The replacement of one base or nucleotide by another  Silent Mutation: Substitution mutation that has no effect  Missense Mutation: Changes of a single nucleotide that does change the amino acid coding  Nonsense Mutation: Change in an amino acid codon into a stop codon

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Frame Shift Either addition or deletion of one or two nucleotide bases. When this occurs, the “reading frame” is changed so that all the codons read after the mutation are incorrect.

Deletion & Insertion  Deletion: To remove one or more nucleotides in a gene  Insertion: Adding one or more nucleotides into a gene Mutations involving the deletion or insertion of one or more nucleotides in a gene often have disastrous effects.

Insertion Deletion

Guess which type of mutation… Normal: The princess looked beautiful in her dress. The princess looked beautiful in dress. The princess looked beatifuli nh erd ress. her u Deletion Frame Shift

Guess which type of mutation… The princess was beautiful in her dress. The princess looked very beautiful in her dress. was looked Substitution Insertion

Types of Chromosomal Mutations  Inversion  Chromosomal Deletion  Translocation  Duplication

Inversion Occurs when a chromosome breaks in two places and the resulting piece of DNA is reversed and re-inserted into the chromosome  Pericentric inversions: inversions that involve the centromere  Paracentric inversions: inversions that do not involve the centromere

Chromosomal Deletion  Occurs when a chromosome breaks and some genetic material is lost

Translocation Chromosomal abnormalities which occur when chromosomes break and the fragments rejoin to other chromosomes  In a balanced translocation, pieces of chromosomes are rearranged but no genetic material is gained or lost in the cell

Duplication A duplication occurs when part of a chromosome is copied (duplicated) abnormally, resulting in extra genetic material from the duplicated segment.

Guess which type of mutation… Normal: The duck swam across the pond. The duck swam across swam across the pond. Duplication The duck swam pond the across. Inversion The duck swam the pond. Chromosomal Deletion across

Guess which type of mutation… Normal: The duck swam across the pond. It looked tiring. The duck looked tiring. It swam across the pond. Translocation

How else do mutations occur?  Errors can occur in the processes of mitosis and meiosis.  Nondisjunction: An accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase.  The result is gametes with abnormal numbers of chromosomes.

Sickle Cell Anemia  Sickle cell anemia is a hereditary disease that causes red blood cells to be shaped like moons.  This is due to a single amino acid substitution in the hemoglobin protein. enome/posters/chromosome/hbb.shtml