91 Questions
What is the term for a mutation that hides or suppresses the effect of another mutation?
Suppressor mutation
What type of mutation restores the wild-type gene and phenotype?
Reverse mutation
What are the sequences that can move about the genome called?
Transposable elements
What is the name for the second mutation in a different gene that fixes the problem caused by the first mutation?
Intergenic mutation
What is the term for a mutation that hides or suppresses the effect of another mutation?
Suppressor mutation
What is the term for the second mutation in the same gene that 'fixes' the problem caused by the first mutation?
Intragenic mutation
What are the sequences that can move about the genome called?
Transposable elements
What is the movement of transposons called?
Transposition
What is the name of the enzyme responsible for cutting out the transposon and separating it?
Transposase
What is the term for the sequences of 9-40 base pairs in length that are inverted complements of each other?
Terminal inverted repeats
How are flanking direct repeats generated during the transposition process?
Cutting and leaving overlapping ends
What type of chromosomal rearrangement is caused by pairing through looping and crossing over between two transposable elements oriented in the same direction?
Deletion
What type of chromosomal rearrangement is caused by pairing through bending and crossing over between two transposable elements oriented in opposite directions?
Inversion
What type of chromosomal rearrangement results from misalignment and unequal exchange between transposable elements located on sister chromatids?
Deletion and duplication
Which type of transposon in bacteria is characterized by genetic material flanked by two insertion sequence elements?
Composite transposons
What is the name of the specific transposable element in eukaryotes that is similar to transposable elements in bacteria and contains short inverted repeats?
DNA transposons
Which bacterial gene insertion can be used as a marker for testing bacterial gene insertions?
Tetracycline resistance
What is the enzyme responsible for copying the ssRNA genome into DNA in retrotransposons?
Reverse transcriptase
What happens to retrotransposons lacking a functional coat protein gene?
They are stuck inside the cell
What kind of events are some transposition events linked to?
Adaptive change
What is the role of mutations in creating variety and evolution?
They create variety necessary for evolution
Which proteins regulate transcription of a gene by binding to a regulatory element that controls that gene?
Helix-turn-helix
What do regulatory genes encode that interact with other sequences and affect the transcription and translation of these sequences?
Transcription factors
What are DNA sequences that play a role in regulating gene expression, often by binding sites for transcription factors?
Regulatory elements
What are DNA sequences that play a role in regulating gene expression, often by binding sites for transcription factors?
Regulatory elements
Which proteins regulate transcription of a gene by binding to a regulatory element that controls that gene?
DNA binding proteins
What type of chromosomal rearrangement is caused by pairing through looping and crossing over between two transposable elements oriented in the same direction?
Tandem duplication
What is the function of a regulator gene in an operon structure?
It encodes products that affect the operon function, but are not part of the operon
What is the role of a separate regulator gene in an operon structure?
It encodes a regulator protein that may bind to the operator site to regulate the transcription of mRNA
What is the defining feature of an operon structure?
Set of co-expressed genes controlled by the same regulatory elements
What is the defining feature of an inducible operon?
It requires a small molecule to turn the gene on
What is the characteristic of a negative repressible operon?
It requires a small molecule to turn the gene off
What is the role of a positive operon?
It involves protein binding to DNA to turn the gene on
What type of operon example does the lac operon exhibit?
Negative inducible operon
What is the regulatory element controlling the lac operon?
Inducer- allolactose
In what conditions does the lac operon function in relation to glucose availability?
When glucose isn’t available
What is the role of allolactose in the lac operon?
It binds to the regulator protein, making it inactive
What happens in the absence of lactose in the lac operon?
The repressor protein binds to the operator, inhibiting transcription
What is the function of the enzyme B-galactosidase in the lac operon?
It breaks lactose into galactose and glucose
What is the function of the regulator protein in the lac operon?
It binds to the operator in the absence of lactose, inhibiting transcription
What is the function of the enzyme B-galactosidase in the lac operon?
It breaks lactose into galactose and glucose
What is the role of allolactose in the lac operon?
It binds to the regulator protein and makes it inactive
What happens in the absence of lactose in the lac operon?
The regulator protein binds to the operator and inhibits transcription
What is the defining feature of a negative repressible operon?
It is usually on and binding of a corepressor inhibits transcription
What type of regulation is the lac operon an example of?
Positive inducible regulation
What prevents the binding of catabolite activator protein (CAP) to the lac operon in the presence of glucose?
Glucose inhibits the production of cAMP
What type of operon is the trp operon of E. coli?
Negative repressible operon
What is the defining characteristic of euchromatin?
Uniform structure
How are structural genes transcribed in eukaryotes?
Each gene has its own promoter and is transcribed separately
What is the role of histone proteins in transcription?
Prevent transcription by tightly binding to DNA
Where does the process of translation occur in eukaryotic cells?
In the cytoplasm
What is the role of histone acetylation in gene expression?
It weakens the interaction between histone proteins and DNA, allowing transcription factors to activate gene expression
How does histone methylation typically affect gene expression?
It often causes gene silencing by repressing transcription
What is the function of histone modification through addition of acetyl groups?
It typically causes relaxation of chromatin, allowing for gene expression
How is gene expression controlled in Arabidopsis through histone acetylation?
Histone acetylation allows transcription factors to activate gene expression
How is DNA methylation maintained through replication?
The DNA is hemi-methylated and methyl groups are added to the unmethylated strand, resulting in fully methylated DNA
What is the effect of histone acetylation on the interaction between histone proteins and DNA?
It weakens the interaction, permitting some transcription factors to bind to DNA
What is the function of an insulator in gene regulation?
It blocks or insulates the effect on enhancers
What is the role of a silencer in gene regulation?
It is a site where repressor proteins bind
What is the function of an enhancer in gene regulation?
It is a DNA sequence stimulating transcription from a distance away from the promoter
What are response elements in gene regulation?
Common regulatory elements upstream of the start site of genes expressed in response to a common environmental stimulus
What is the role of microRNAs in gene expression regulation?
MicroRNAs inhibit translation by pairing imperfectly with mRNA sequences
What is the function of small interfering RNAs (siRNAs) in gene expression regulation?
SiRNAs combine with protein complex RISC and pair with complementary sequences on mRNA to degrade RNA
How does RNA interference (RNAi) influence transcription of DNA?
SiRNAs attach to complementary sequences in DNA and attract methylating enzymes which methylate the DNA or histones and inhibit transcription
What is the role of dicer in RNA cleavage?
Dicer cleaves double-stranded RNA to produce small interfering RNAs and microRNAs
What is the outcome of microRNAs pairing imperfectly with an mRNA sequence?
Inhibition of translation
How do some siRNAs influence transcription of DNA?
Attach to complementary sequences in DNA and attract methylating enzymes, leading to methylation of DNA or histones
What is the defining characteristic of a benign tumor?
Tumor remains localized
What is the function of the G0 phase in the cell cycle?
The cell enters a non-dividing phase
What occurs during the S phase of the cell cycle?
DNA duplicates
What happens at the G2/M checkpoint in the cell cycle?
The cell prepares for mitosis
What is the role of cyclins in the cell cycle?
They bind to and activate cyclin-dependent kinases
What is the function of oncogenes in the cell cycle?
They act as gas pedals, promoting cell division
What leads to cancer due to mutations in the cell cycle?
Mutations in tumor suppressors
Which checkpoint regulates the decision point on whether to replicate DNA?
G1/S checkpoint
What regulates the Mitosis promoting factor (MPF) in the G2/M checkpoint?
Cyclin B
What is the phase of the cell cycle that involves the separation of sister chromatids?
Mitosis
What are oncogenes?
Mutated, dominant-acting, stimulatory genes that cause cancer
How do tumor suppressor genes contribute to cancer?
Mutated recessive-acting inhibitory genes that are inactive
What is the role of proto-oncogenes in normal cells?
Responsible for basic cellular functions
How do retroviruses cause cancer?
By mutating and rearranging proto-oncogenes
What is the main difference between forward and reverse genetics?
Forward genetics involves identifying a gene mutation based on an interesting phenotype, while reverse genetics involves mutating a gene of interest to observe resulting phenotype
How did the Nobel Prize recipients from 2007 insert targeted mutations to alter a genome?
By using CRISPR-Cas9 technology
What is the primary approach of reverse genetics?
Mutating a gene of interest to observe resulting phenotype
What is CRISPR-Cas9 comprised of?
A single guide RNA and a nuclease that attach to specific DNA sequences and make double-stranded cuts
Which repair mechanism introduces specific changes to the genome?
Homology-directed repair
What occurs during non-homologous end joining repair?
Small, random mistakes in the fusion of DNA ends
What is the outcome of homology-directed repair?
Introduction of specific changes to the genome
What happens when Cas9 is mutated to only cut one strand?
It requires two different gRNAs to target one locus, reducing off-target effects
What is the result of fusing Cas9n with reverse transcriptase?
RNA has both the targeting sequence and the sequence to be inserted
What is the function of dead Cas9 or Cas9n fused with deaminase protein domain?
Cytosine turns into uracil, acting like thymine
Test your knowledge of genetics and mutations with this quiz on suppressor mutations. Challenge yourself to understand how forward and reverse mutations work, and learn about intragenic mutations within the same gene. See how well you grasp the concept of mutations and their effects on gene expression.
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