88 Questions
What is the characteristic of euchromatin in metabolically active cells?
Loosely packed and diffuse
What is the term for the chromatin region that can transition to and from a relaxed state?
Facultative heterochromatin
What is the characteristic of heterochromatin in terms of gene expression?
Transcriptionally inactive
What is the term for the chromatin region that is always in a condensed state?
Constitutive heterochromatin
What is the characteristic of heterochromatin in terms of G-banding?
Stains more darkly
What is the term for the region of chromatin that is highly compact and shows up as dark spots in G-banding?
Heterochromatin
What is the primary mechanism by which rho-independent transcription termination occurs in prokaryotes?
The formation of a hairpin loop structure in the RNA transcript
What is the function of the rho helicase enzyme in rho-dependent transcription termination?
To inactivate the elongation complex
What is the role of the G:C-rich regions in rho-independent transcription termination?
They are transcribed into RNA and fold into a short double-stranded hairpin
What is the primary cause of transcription termination in rho-independent transcription termination?
The dissociation of the elongation complex
What is the characteristic of the specific sequence in the mRNA that causes transcription termination in rho-independent transcription termination?
It contains inverted repeats
What is the outcome of the formation of a hairpin loop structure in the RNA transcript during rho-independent transcription termination?
The elongation complex dissociates
What type of enzymes are small nuclear ribonucleoproteins (snRNPs) that participate in the splicing process?
protein-RNA
What is the function of the branch point in the splicing process?
To interact with snRNA and cut the mRNA
What is the sequence at the 5'-end of an intron?
GU
What is the function of the spliceosome in the splicing process?
To remove introns from the pre-mRNA
Where is the acceptor site located in the splicing process?
At the 5'-end of an exon
What is the result of the splicing process?
The removal of an intron and the joining of exons
What is the primary function of the 5' cap in eukaryotic mRNA?
To protect the mRNA from 5' exonucleases
What is the result of a nonsense variant in a DNA sequence?
A substitution that leads to a premature stop codon
What is the enzyme responsible for adding a bisphosphate group to the 5' mRNA terminal?
RNA triphosphatase
What is the size range of chromosomal variants?
1-5 Mb
During transcription of pre-mRNA in eukaryotes, what is the primary function of RNA polymerase?
To elongate the transcript along the DNA template
What is the result of a substitutional change from A to UAG in a DNA sequence?
A nonsense mutation that introduces a premature stop codon
What is the term for the unusual pyrophosphate bridge at the 5' terminus of eukaryotic mRNA?
5'-5' pyrophosphate bridge
What is the term for a variant that involves the duplication of a DNA sequence?
Duplication
What is the purpose of the methyl group added to the 7-nitrogen of guanine in the 5' cap?
To provide a recognition signal for the translational apparatus
What is the term for a short sequence of nucleotides that is repeated in a tandem array?
Microsatellite
What is the difference between prokaryotic and eukaryotic mRNA in terms of processing?
Eukaryotic mRNA requires processing, whereas prokaryotic mRNA does not
What is the term for a type of genetic variant that involves the insertion or deletion of one or a few nucleotides?
Insertion/deletion (Indel)
What is the percentage of total cellular RNA composed of tRNA?
10%
What is the location of the anticodon loop on tRNA?
Anticodon loop is present on mRNA
What is the molecular weight range of tRNA?
10,000 - 31,000
What is the characteristic of the secondary structure of tRNA?
Cloverleaf structure
Where is tRNA predominantly located in the cell?
Cell cytoplasm
What is the approximate length of DNA that wraps around the core histone octamer in a nucleosome?
147 bp
What is the role of the H1 protein in chromatin architecture?
Stabilization of both nucleosome structure and higher-order chromatin architecture
What is the size of the chromatin fiber that is formed after the coiling of the 30-nm chromatin fiber?
250-nm wide fiber
What is the term for the stretch of DNA that links the histone cores in a nucleosome?
Linker DNA
How many complete turns of DNA does the 30-nm chromatin fiber make around the nucleosome?
2 complete turns
What is the purpose of the histone octamer in DNA packaging?
To compact DNA into chromatin fibers
What is the primary function of chromatin in heterochromatic regions?
To silence genes by compacting them
What is the characteristic of chromatin in euchromatic regions?
It is loosely packed and associated with active transcription
What is the difference between facultative and constitutive heterochromatin?
Facultative heterochromatin is reversible, while constitutive heterochromatin is always in a condensed state
What is the characteristic of repetitive sequences in heterochromatic regions?
They are not transcribed and are rich in gene silencing sequences
What is the relationship between chromatin structure and gene expression?
Tightly wound chromatin is associated with active transcription, while loosely packed chromatin is associated with gene silencing
What is the characteristic of chromatin in centromeric regions?
It is tightly wound and gene-poor
What is the result of the resolvase enzyme cutting at the Holliday junctions?
The two original portions of each chromosome upstream and downstream from the two Holliday junctions are swapped
What is the primary difference between apoptosis and necrosis?
Apoptosis is a regulated process, whereas necrosis is unregulated
What is the outcome of a cell that dies through necrosis?
The cell is rapidly eliminated, releasing its contents and causing tissue damage
What is the purpose of apoptosis in multicellular organisms?
To eliminate damaged or infected cells that could threaten the health of the organism
What is the characteristic of apoptosis in terms of the fate of the cell?
The cell is eliminated in a controlled manner
What is the primary consequence of failing to pass the G1 checkpoint in the cell cycle?
Cells may be signaled to undergo apoptosis
What is the primary function of the G2 checkpoint in the cell cycle?
To ensure proper cell signaling for mitosis
What is the consequence of a cell having damaged DNA during the G1 checkpoint?
The cell undergoes DNA repair mechanisms
What is the role of signals in the G1 and G2 checkpoints?
To signal the cell to proceed to the next phase
What is the consequence of a cell having inadequate nutrients during the G1 checkpoint?
The cell arrests in the G1 phase
What is the primary function of apoptosis during the cell cycle?
To eliminate damaged or unwanted cells
On which strand of DNA replication is synthesis continuous?
Leading strand
What is the location of the L-strand origin of replication in the mitochondrial genome?
Outside the noncoding region, within a tRNA cluster
What is the role of the mitochondrial DNA-directed RNA polymerase (POLRMT)?
Initiates primer synthesis
What is the primary component of nucleotides?
A 5-carbon sugar
What is the term for the short H-strand replication product formed by premature termination of nascent H-strand DNA synthesis at the termination-associated sequence?
7S DNA
What is the difference between a nucleoside and a nucleotide?
A nucleotide has a phosphate group, while a nucleoside does not
What is the type of sugar found in DNA?
Deoxyribose
How many mRNA molecules are encoded in the mitochondrial genome?
13
What is the term for the process of attaching a phosphate group to a nucleoside?
Phosphorylation
What is the purpose of the conserved sequence boxes (CSB1-3) in the noncoding region of the mitochondrial genome?
Their function is not clearly understood
What is the term for the type of RNA that contains the genetic information?
mRNA
What is the component of nucleic acids that is responsible for the transmission of genetic traits?
Nitrogenous bases
What is the characteristic of the mt-rRNA and mt-tRNA molecules?
They are small
What is the role of the D-loop region in mtDNA?
It is a regulatory region for mtDNA expression
What is the source of the protein components required for mitochondrial translation?
Nuclear genome-encoded genes
What is the characteristic of the mtDNA genome?
It is a circular DNA molecule
What is the result of polyadenylation of the mRNAs in mtDNA?
Generation of termination codons
What is the location of the hypervariable regions in mtDNA?
In the D-loop region
What is the primary function of Spo11 protein in homologous recombination?
To break both strands of the DNA double helix
What is the role of Mre11 nuclease in homologous recombination?
To degrade the ends of the broken DNA
What is the outcome of the interaction between the protein-DNA filament and the sister chromatid?
Formation of a double Holliday junction
What is the function of DNA polymerase in homologous recombination?
To extend the 3’ overhangs of the broken DNA
What is the outcome of the resolution of the double Holliday junction?
Generation of new genetic combinations
What is the primary function of RecA protein in homologous recombination?
To bind to the 3’ overhangs and form a protein-DNA filament
What is the outcome of the activation of the extrinsic pathway of apoptosis?
The controlled death of the cell
What is the role of cytochrome c in the intrinsic pathway of apoptosis?
To form a complex with Apaf1 and oligomerize into a wheel-like heptamer
What is the function of the death-inducing signaling complex (DISC) in the extrinsic pathway of apoptosis?
To form a complex with Fas ligand and activate the extrinsic pathway of apoptosis
What is the key difference between the extrinsic and intrinsic pathways of apoptosis?
The type of signal that activates the pathway
What is the role of Apaf1 in the intrinsic pathway of apoptosis?
To form a complex with cytochrome c and oligomerize into a wheel-like heptamer
What is the outcome of the cleavage of key proteins by the executioner caspases in the apoptosis pathway?
The cell dies in a controlled manner
Test your understanding of the chromatin fiber, its compaction, and the different forms of heterochromatin, including facultative and constitutive heterochromatin. Learn about gene silencing and the characteristics of these chromatin regions.
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