1. Relationship between Genotype and Phenotype
Molecular Basis for
Relationship between Genotype and Phenotype
genotype
DNA
DNA sequence
transcription
RNA
translation
amino acid
sequence
protein
function
phenotype
organism

2. Frameshift Mutations and Suppressor Mutations
frameshift mutations: insertions or deletions of nucleotides that cause a shift in the translational reading frame
suppressor mutations: mutations that counteract or suppress the effects of another mutation
wild-type
CAU CAU CAU CAU CAU
HIS HIS HIS HIS HIS
addition of A
deletion of A
CAU ACA UCA UCA UCA U__
HIS THR SER SER SER
CAU ACU CAU CAU CAU
HIS THR HIS HIS HIS
deletion of U
addition of G
CAU CAC AUC AUC AU__
HIS HIS ILE ILE
CAU CAC GAU CAU CAU
HIS HIS ASP HIS HIS

3. Mutation: Levels of Hereditary Change
Gene (Point) Mutation:
One allele changes to a different allele.
Effects are limited to that locus.
Chromosome Mutation:
Changes occur at the chromosome level.
Multi-locus effects are not unusual.

4. Relationship between Genotype and Phenotype
Molecular Basis for
Relationship between Genotype and Phenotype
genotype
DNA
DNA sequence
transcription
RNA
translation
amino acid
sequence
protein
function
phenotype
organism

5. Base substitution: change in base of nucelotide pair
Point mutations at the molecular level
Base substitution: change in base of nucelotide pair
Base additions: insertion of nucleotide pairs
Base deletions: deletion of nucleotide pairs

6. Point mutations at the molecular level

7. Consequences of Point Mutations within Genes

8. Point Mutations Can Alter mRNA Splicing

9. Point Mutations on Gene Products

10. Mutation frequencies obtained with various mutagens in Neurospora
Mutagens are agents that cause mutations. Anything that is capable of causing chemical changes in the structure of DNA (especially bases) is a mutagen.
Mutagens differ in mutagenicity.

11. The Ames Test Reveals Mutagenic Compounds
Strain 1 - frameshift mutation
Strain 2 - base substitution

12. Revertant colonies per culture plate.
Ames Test Results1
Revertant colonies per culture plate.
Treatment
Control
diethyl sulfate*
ICR-191**
TA1575 11
14,700 13
TA1578 25
450
TA1575 : his base substitution mutant
TA1578 : his frameshift mutant
* Highly toxic alkylating agent, occurs as colorless liquid with peppermint odor
** Acridine, colorless solid intercalating agent, known carcinogen
1 McCann et al., Proc. Natl. Acad. Sci. USA