Mutations Sometimes cells make mistakes copying there own

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Mutations

Mutations

Sometimes cells make mistakes copying there own DNA during the replication process in mitosis.

Sometimes cells make mistakes copying there own DNA during the replication process in mitosis. l They can insert an incorrect base or skip a base. l This mistake is called a mutation. l Mutations - changes in the DNA sequence that affects genetic information. l There are several types of mutations: gene and chromosomal.

Gene Mutations l Most gene mutations involve one nucleotide, but occasionally several are involved.

Gene Mutations l Most gene mutations involve one nucleotide, but occasionally several are involved. l Point Mutations is a mutations involving one nucleotide and they occur at a single point on the DNA molecule. l 1) One nucleotide is substituted for another, often changing the resulting Amino Acid and potentially the protein produced.

Some point mutations simply substitute one nucleotide (GCAT) for another. l As a result,

Some point mutations simply substitute one nucleotide (GCAT) for another. l As a result, one amino acid may be changed in the large protein. l When the point mutation involves the insertion of an extra nucleotide or deletion of one that already exits, bigger changes can occur. l Remember the genetic code is read in groups of three nitrogenous bases (nucleotides) or codons. l l The result of an insertion or deletion is called a frameshift mutation. Result: larger changes in what’s “produced” will occur.

A frameshift mutation occurs because the insertion or deletion causes a shift in the

A frameshift mutation occurs because the insertion or deletion causes a shift in the reading frame of the genetic material. l It can affect every amino acid that follows the insertion or deletion and change the entire protein (polypeptide). l As a result, the protein may not be able to perform its normal function. l l l Normal sequence: Deletion: ATT-GCC-GTA…. _TTG-CCG-TAC…. l l Normal sequence: ATT-GCC-GTA…. Insertion: GAT-TGC-CGT-A…. .

Gene Mutations: Substitution, Insertion, and Deletion (frameshift mutations) Substitution Go to Section: Insertion Deletion

Gene Mutations: Substitution, Insertion, and Deletion (frameshift mutations) Substitution Go to Section: Insertion Deletion

Chromosomal Mutations l Chromosomal mutations involve changes in the number or structure of chromosomes.

Chromosomal Mutations l Chromosomal mutations involve changes in the number or structure of chromosomes. l Changes may include: l locations of genes on chromosomes, l number of copies of genes.

Four types of chromosomal mutations. l 1. deletion: loss of all or part of

Four types of chromosomal mutations. l 1. deletion: loss of all or part of a chromosome. l 2. duplication: opposite of deletion in which a segment of the chromosome is repeated. l 3. inversion: part of the chromosome gets oriented in reverse of its usual direction. l 4. translocation: part of one chromosome breaks off and attaches to another chromosome.

Chromosomal Mutations Deletion Duplication Inversion Translocation

Chromosomal Mutations Deletion Duplication Inversion Translocation

l Remember all cells of an organism are genetically identical (their DNA is exactly

l Remember all cells of an organism are genetically identical (their DNA is exactly the same) l What type of cell it is depends whether or not a particular gene has been turned “on” or not

Typical Gene Structure Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand

Typical Gene Structure Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand Stop transcription

What causes DNA mutations? l l l l Ultraviolet light (solar radiation/sun) nuclear radiation,

What causes DNA mutations? l l l l Ultraviolet light (solar radiation/sun) nuclear radiation, X-rays chemicals in the environment can damage DNA by altering nucleotide bases so that they look like other nucleotide bases. DNA get copied wrong during replication or protein synthesis causing big problems. Cancer can be a result. Some mutations cause healthy changes too and lead to evolution of the species.

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