mutations natural and artificial mutations. mutations there are 2 classes of mutations nucleotide...

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Mutations Natural and Artificial Mutations

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Page 1: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Mutations

Natural and Artificial Mutations

Page 2: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Mutations

There are 2 classes of mutations Nucleotide mutations occur when 1-4

nucleotides are altered, added or removed as a result of damage or errors in replication

Transpositions occur when entire sections of DNA “jump” to a different location in the DNA, disrupting genes

Page 3: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Examples of nucleotide mutations Point Mutations – one nucleotide is altered Silent Mutation: CTC to CTT – no change since both

codons code for glutamic acid Missense Mutation: CTC to CTA replaces glutamic

acid with aspartic acid in hemoglobin since they are functionally similar amino acids, the

protein is not greatly affected and the mutation introduces a variation in the species

CTC to CAC replaces glutamic acid with valine Valine is hydrophobic and results in clumping of

hemoglobin, resulting in sickle cell anemia

Page 4: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Sickle Cell Anemia

Page 5: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Nucleotide Mutations

A point mutation could also result in the production of a stop codon in the middle of a gene

If this occurs in an essential protein, such as hemoglobin, the mutation is lethal and is called a nonsense mutation

Frameshift mutations are also normally lethal – the insertion or deletion of a nucleotide shifts the entire reading frame and every codon is altered

Page 6: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Transposons

Page 7: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Transposons

Page 8: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Transposons

Approximately 50 % of the human genome is made up of transposons

They can “jump” from one location to another, or they can copy themselves first, and the copy jumps

Transposons can cause mutations by inserting themselves into exons, or by taking exons with them; “shuffling” the genetic deck

Transposons can jump to a promoter region and either turn off or turn up transcription

Page 9: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Transposons

Page 10: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Artificial Mutation

Page 11: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

UV Radiation

UV radiation produces covalent bonds between adjacent thymine base pairs

These dimers block replication by DNA polymerase Cells can repair the damage by removing the

damaged section on one side of the helix DNA polymerase and DNA ligase complete the

repair If the repair is done incorrectly, a mutation results

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Page 12: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Chemical Mutagens

Base analogs Chemicals that have a

very similar structure to thymine, uracil, adenine, cytosine or guanine

Example: 5’bromouracil Base analogs generally

result in point mutations

Page 13: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Chemical Mutagens

Acridine dyes These chemicals have

a positive charge so they bind to the negatively charged DNA

They insert between base pairs and cause frameshift mutations

Examples; nitrous acid and hydrazine

Page 14: Mutations Natural and Artificial Mutations. Mutations There are 2 classes of mutations Nucleotide mutations occur when 1-4 nucleotides are altered, added

Chemical Mutagens

Alkylating agents Can transfer methyl groups,

ethyl groups, bond with phosphate groups

This can result in any type of mutation, including the lethal breakage of the DNA sugar-phosphate backbone

They are actually used as chemotherapy in the treatment of cancer, destroying the cancerous cells’ DNA

Image from Science Daily