Chapter 10-Genetics Flashcards
Mutation
Heritable change in the base sequence of the genome of an organism
Mutant
Organism with a mutation, genotype differs from parents
Wild-type
Isolated from nature, can be gene or strain
What are some examples of genotype vs. phenotype? How do these examples relate to mutations?
The gene for histodinol phosphate aminotransferase, hisC codes for the protein HisC. Mutations in this gene are hisCI and hisC2
His+ and His- do different actions
What does His+ do?
Makes own histodine (histodine prototroph)
What does His- do?
Cannot make own histidine, requires histidine supplement (histidine auxotroph)
Mutant selection
Placing organisms under conditions that favor or inhibit growth of cells with certain phenotypes
Mutant screening
Procedure to evaluate many strains, but all strains are able to grow
Is antibiotics resistance selectable or screening?
It’s selectable
Is pigment production selectable or screening?
Must screen
What are two molecular bases for mutation?
- Induced-environmental cause
2. Spontaneous-errors in DNA replication
Transition
a point mutation that changes a purine nucleotide to another purine (A ↔ G) or a pyrimidine nucleotide to another pyrimidine (C ↔ T).
Transversion
the substitution of a (two ring) purine for a (one ring) pyrimidine or vice versa, in deoxyribonucleic acid (DNA).[1]
Frameshifts are due to what?
Due to insertions or deletions
Reversion
“Back mutation” that restores the original phenotype
Same-site revertant
Mutation at same site restores phenotype
Second-site revertant
Mutation at different site in DNA restores phenotype-supressor mutation
Supressor mutations
- Mutations in same gene (2nd frameshift mutation)
- Mutation in another gene that restores function
- Mutation in another gene that replaces non-functional enzyme with a functional one
Deletions, frameshift mutations are…
stable
Insertions are…
not as stable
What is removed during direct reversal during DNA repair?
An alkyl group
What are three ways of DNA repair?
- Direct reversal
- Repair of single-stranded damage
- Repair of double-strand damage
In addition to the removal of an alkyl group, what also happens during direct reversal?
Photoreactivation, which cleaves pyrimidine dimers