Exam 2 Study Guide S21-1 (1) Flashcards
(35 cards)
What are point mutations?
Mutations that involve a change in a single nucleotide in the DNA sequence
Includes transitions and transversions, typically occurring in a 2:1 ratio in nature.
What are the types of structural gene mutations?
- Silent
- Missense
- Nonsense
- Frameshift
Each type affects the protein product differently.
What are suppressor mutations?
- Intragenic
- Intergenic
These mutations can counteract the effects of other mutations.
Can mutations affect non-coding sequences?
Yes, they can affect phenotypes through changes in promoters, regulatory elements, UTR, and splice sites.
What are the phenotypic types of mutations?
- Deleterious
- Beneficial
- Conditional
- Neutral
Each type has a different impact on the organism’s fitness.
Are mutations random and directed?
No, mutations are random and not directed or adaptive.
This is supported by the Luria-Delbruck fluctuation test and Lederberg replica plating.
What are spontaneous mutations?
- DNA replication errors
- Repeat expansion
- Depurination of purines
- Deamination of cytosines
- Tautomeric shifts
- Reactive oxygen species (ROS)
These occur naturally without external influence.
What are induced mutagens?
- Chemical mutagens (e.g., base modifiers, base analogues, intercalating agents)
- Physical mutagens (e.g., ionizing radiation, non-ionizing radiation such as UV)
Induced by environmental factors.
What types of repair mechanisms exist for DNA mutations?
- Base excision repair
- Nucleotide excision repair
- Methyl-directed mismatch repair
- Photolyase removal of pyrimidine dimers
- Recombination repair
Diseases like Xeroderma pigmentosum are caused by defects in these mechanisms.
What is an operon?
A group of genes under the control of a single promoter, allowing coordinated regulation of genes with a common functional goal.
What is the difference between positive and negative control in gene regulation?
- Positive control: regulated by activation
- Negative control: regulated by repression
These mechanisms determine how genes are expressed.
What is catabolic regulation?
A type of regulation that uses induction, exemplified by the lac operon.
What is anabolic regulation?
A type of regulation that uses inhibition, exemplified by the trp operon.
What is the lac operon?
A polycistronic mRNA that includes genes such as lac Z (β-galactosidase) and lac Y (permease).
It is regulated by a repressor (lac I) and an activator (CAP).
What is the role of allolactose in the lac operon?
It acts as an inducer that binds to the repressor, allowing transcription to occur.
What is the trp operon?
A polycistronic mRNA regulated by negative control, where the corepressor is tryptophan.
What is attenuation in the trp operon?
A mechanism allowing premature termination of transcription based on tryptophan levels.
What are riboswitches?
Structural elements in mRNA that can influence transcription and translation.
What are transcription factors?
Proteins that bind to specific DNA sequences to regulate gene expression.
What is chromatin remodeling?
The process of altering chromatin structure to allow for gene expression.
What is the role of DNA methylation?
Generally inhibits expression and is involved in chromatin compaction, repair, and genomic imprinting.
What is alternative splicing?
A process that allows a single gene to produce multiple mRNA variants.
What are homologous chromosomes?
Chromosome pairs, one from each parent, that are similar in shape, size, and genetic content.
What is the significance of the kinetochore?
It is the structure where microtubules attach during cell division.
