mutation and mutagens.notebook February 28, 2012 Mutations and Mutagens
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mutation and mutagens.notebook February 28, 2012
Mutations and Mutagens
mutation and mutagens.notebook February 28, 2012
A mutation is an alteration of a gene’s DNA sequence that can result in changes to the protein that the mutated gene codes for.
• In order to be passed on to future generations, mutations must occur to the DNA in the sex cells.• Mutations in the somatic cells will only affect the organism in which the mutation originally occurs
mutation and mutagens.notebook February 28, 2012
Types of MutationsPoint Mutations These mutations affect only one or a few nucleotides due to a chemical change.
Nucleotide substitutionsThis happens when one nucleotide is replaced by another and incorrect base pairing occurs
For example, ATTCGG could change to ATTCGT
mutation and mutagens.notebook February 28, 2012
The effects may be minor (silent mutations)Either the amino acid does not change, or the change is so minimal that it doesn’t affect the structure or function of the protein.
What can happens to a gene when a nucleotide changes?
Yay Wobble!
mutation and mutagens.notebook February 28, 2012
The substituted nucleotide causes a fairly significant change in the protein, which can affect the health of the organism (either negatively or positively)
Example of a negative effect: sickle cell anemia results from the change of one amino acid that codes for the proteins that make up hemoglobin
Example of a positive effect: some missense mutations allow for the production of a variety of antibodies, improving our immune systems
The effects may be somewhat harmful (missense mutations)
mutation and mutagens.notebook February 28, 2012
The effects may have severe consequences (non sense mutation)
The substitution of a nucleotide in the start and stop codons may result in the inability to code for any functional protein at all
mutation and mutagens.notebook February 28, 2012
These mutations involve the insertion or deletion of one or two nucleotides.
This impacts the codons from the point of the mutation to the end of the gene.The entire reading frame of the gene is shifted.
Frameshift mutations
mutation and mutagens.notebook February 28, 2012
Chromosomal MutationsMay affect more than one gene because of the rearrangement of the genetic material
During replication or meiosis, sections are switched, lost, moved or incorrectly duplicated
mutation and mutagens.notebook February 28, 2012
Causes of MutationsSpontaneous Mutations
Take place naturallyInduced Mutations
Caused by agents outside the cell called mutagens
mutation and mutagens.notebook February 28, 2012
Physical MutagensHigh energy (Xray) radiation breaks through the DNA strand
Causes the deletion of a few nucleotides, or even the destruction of large portions of the chromosome
Lower energy (UV) radiation Affects C and TAffects DNA replicationCan lead to skin cancers
mutation and mutagens.notebook February 28, 2012
Chemical MutagensReacts chemically with the DNA moleculeMost chemical mutagens are carcinogenic
mutation and mutagens.notebook February 28, 2012
Cumulative MutagensIndividually, small mutations may not have an obvious effectHowever, the combination of a number of small mutations over time may result in significant effects
mutation and mutagens.notebook February 28, 2012
Mutation Repair MechanismsReview the various mechanisms for mutation repair. Add them to your note. Answer p. 292 # 1, 2, 6
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