Chromatin Structure and Heterochromatin

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What is the characteristic of euchromatin in metabolically active cells?

Tightly wound and highly compacted

Transcriptionally inactive

Loosely packed and diffuse (correct)

Rich in repetitive sequences

What is the term for the chromatin region that can transition to and from a relaxed state?

Facultative heterochromatin (correct)

Heterochromatic region

Euchromatin

Constitutive heterochromatin

What is the characteristic of heterochromatin in terms of gene expression?

Actively transcribed

Rich in repetitive sequences

Loosely packed and diffuse

Transcriptionally inactive (correct)

What is the term for the chromatin region that is always in a condensed state?

Constitutive heterochromatin (A) Signup and view all the answers

What is the characteristic of heterochromatin in terms of G-banding?

Stains more darkly (C) Signup and view all the answers

What is the term for the region of chromatin that is highly compact and shows up as dark spots in G-banding?

Heterochromatin (B) Signup and view all the answers

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 (B) Signup and view all the answers

What is the function of the rho helicase enzyme in rho-dependent transcription termination?

To inactivate the elongation complex (D) Signup and view all the answers

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 (C) Signup and view all the answers

What is the primary cause of transcription termination in rho-independent transcription termination?

The dissociation of the elongation complex (A) Signup and view all the answers

What is the characteristic of the specific sequence in the mRNA that causes transcription termination in rho-independent transcription termination?

It contains inverted repeats (D) Signup and view all the answers

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 (B) Signup and view all the answers

What type of enzymes are small nuclear ribonucleoproteins (snRNPs) that participate in the splicing process?

protein-RNA (A) Signup and view all the answers

What is the function of the branch point in the splicing process?

To interact with snRNA and cut the mRNA (A) Signup and view all the answers

What is the sequence at the 5'-end of an intron?

GU (A) Signup and view all the answers

What is the function of the spliceosome in the splicing process?

To remove introns from the pre-mRNA (D) Signup and view all the answers

Where is the acceptor site located in the splicing process?

At the 5'-end of an exon (D) Signup and view all the answers

What is the result of the splicing process?

The removal of an intron and the joining of exons (D) Signup and view all the answers

What is the primary function of the 5' cap in eukaryotic mRNA?

To protect the mRNA from 5' exonucleases (A) Signup and view all the answers

What is the result of a nonsense variant in a DNA sequence?

A substitution that leads to a premature stop codon (A) Signup and view all the answers

What is the enzyme responsible for adding a bisphosphate group to the 5' mRNA terminal?

RNA triphosphatase (C) Signup and view all the answers

What is the size range of chromosomal variants?

1-5 Mb (D) Signup and view all the answers

During transcription of pre-mRNA in eukaryotes, what is the primary function of RNA polymerase?

To elongate the transcript along the DNA template (C) Signup and view all the answers

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 (A) Signup and view all the answers

What is the term for the unusual pyrophosphate bridge at the 5' terminus of eukaryotic mRNA?

5'-5' pyrophosphate bridge (D) Signup and view all the answers

What is the term for a variant that involves the duplication of a DNA sequence?

Duplication (A) Signup and view all the answers

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 (A) Signup and view all the answers

What is the term for a short sequence of nucleotides that is repeated in a tandem array?

Microsatellite (A) Signup and view all the answers

What is the difference between prokaryotic and eukaryotic mRNA in terms of processing?

Eukaryotic mRNA requires processing, whereas prokaryotic mRNA does not (C) Signup and view all the answers

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) (C) Signup and view all the answers

What is the percentage of total cellular RNA composed of tRNA?

10% (B) Signup and view all the answers

What is the location of the anticodon loop on tRNA?

Anticodon loop is present on mRNA (A) Signup and view all the answers

What is the molecular weight range of tRNA?

10,000 - 31,000 (C) Signup and view all the answers

What is the characteristic of the secondary structure of tRNA?

Cloverleaf structure (A) Signup and view all the answers

Where is tRNA predominantly located in the cell?

Cell cytoplasm (C) Signup and view all the answers

What is the approximate length of DNA that wraps around the core histone octamer in a nucleosome?

147 bp (C) Signup and view all the answers

What is the role of the H1 protein in chromatin architecture?

Stabilization of both nucleosome structure and higher-order chromatin architecture (C) Signup and view all the answers

What is the size of the chromatin fiber that is formed after the coiling of the 30-nm chromatin fiber?

250-nm wide fiber (C) Signup and view all the answers

What is the term for the stretch of DNA that links the histone cores in a nucleosome?

Linker DNA (A) Signup and view all the answers

How many complete turns of DNA does the 30-nm chromatin fiber make around the nucleosome?

2 complete turns (D) Signup and view all the answers

What is the purpose of the histone octamer in DNA packaging?

To compact DNA into chromatin fibers (C) Signup and view all the answers

What is the primary function of chromatin in heterochromatic regions?

To silence genes by compacting them (D) Signup and view all the answers

What is the characteristic of chromatin in euchromatic regions?

It is loosely packed and associated with active transcription (B) Signup and view all the answers

What is the difference between facultative and constitutive heterochromatin?

Facultative heterochromatin is reversible, while constitutive heterochromatin is always in a condensed state (B) Signup and view all the answers

What is the characteristic of repetitive sequences in heterochromatic regions?

They are not transcribed and are rich in gene silencing sequences (A) Signup and view all the answers

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 (B) Signup and view all the answers

What is the characteristic of chromatin in centromeric regions?

It is tightly wound and gene-poor (A) Signup and view all the answers

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 (C) Signup and view all the answers

What is the primary difference between apoptosis and necrosis?

Apoptosis is a regulated process, whereas necrosis is unregulated (D) Signup and view all the answers

What is the outcome of a cell that dies through necrosis?

The cell is rapidly eliminated, releasing its contents and causing tissue damage (C) Signup and view all the answers

What is the purpose of apoptosis in multicellular organisms?

To eliminate damaged or infected cells that could threaten the health of the organism (C) Signup and view all the answers

What is the characteristic of apoptosis in terms of the fate of the cell?

The cell is eliminated in a controlled manner (B) Signup and view all the answers

What is the primary consequence of failing to pass the G1 checkpoint in the cell cycle?

Cells may be signaled to undergo apoptosis (D) Signup and view all the answers

What is the primary function of the G2 checkpoint in the cell cycle?

To ensure proper cell signaling for mitosis (C) Signup and view all the answers

What is the consequence of a cell having damaged DNA during the G1 checkpoint?

The cell undergoes DNA repair mechanisms (A) Signup and view all the answers

What is the role of signals in the G1 and G2 checkpoints?

To signal the cell to proceed to the next phase (C) Signup and view all the answers

What is the consequence of a cell having inadequate nutrients during the G1 checkpoint?

The cell arrests in the G1 phase (A) Signup and view all the answers

What is the primary function of apoptosis during the cell cycle?

To eliminate damaged or unwanted cells (D) Signup and view all the answers

On which strand of DNA replication is synthesis continuous?

Leading strand (A) Signup and view all the answers

What is the location of the L-strand origin of replication in the mitochondrial genome?

Outside the noncoding region, within a tRNA cluster (A) Signup and view all the answers

What is the role of the mitochondrial DNA-directed RNA polymerase (POLRMT)?

Initiates primer synthesis (B) Signup and view all the answers

What is the primary component of nucleotides?

A 5-carbon sugar (B) Signup and view all the answers

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 (D) Signup and view all the answers

What is the difference between a nucleoside and a nucleotide?

A nucleotide has a phosphate group, while a nucleoside does not (C) Signup and view all the answers

What is the type of sugar found in DNA?

Deoxyribose (C) Signup and view all the answers

How many mRNA molecules are encoded in the mitochondrial genome?

13 (D) Signup and view all the answers

What is the term for the process of attaching a phosphate group to a nucleoside?

Phosphorylation (D) Signup and view all the answers

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 (C) Signup and view all the answers

What is the term for the type of RNA that contains the genetic information?

mRNA (A) Signup and view all the answers

What is the component of nucleic acids that is responsible for the transmission of genetic traits?

Nitrogenous bases (B) Signup and view all the answers

What is the characteristic of the mt-rRNA and mt-tRNA molecules?

They are small (D) Signup and view all the answers

What is the role of the D-loop region in mtDNA?

It is a regulatory region for mtDNA expression (D) Signup and view all the answers

What is the source of the protein components required for mitochondrial translation?

Nuclear genome-encoded genes (C) Signup and view all the answers

What is the characteristic of the mtDNA genome?

It is a circular DNA molecule (B) Signup and view all the answers

What is the result of polyadenylation of the mRNAs in mtDNA?

Generation of termination codons (A) Signup and view all the answers

What is the location of the hypervariable regions in mtDNA?

In the D-loop region (C) Signup and view all the answers

What is the primary function of Spo11 protein in homologous recombination?

To break both strands of the DNA double helix (D) Signup and view all the answers

What is the role of Mre11 nuclease in homologous recombination?

To degrade the ends of the broken DNA (D) Signup and view all the answers

What is the outcome of the interaction between the protein-DNA filament and the sister chromatid?

Formation of a double Holliday junction (D) Signup and view all the answers

What is the function of DNA polymerase in homologous recombination?

To extend the 3’ overhangs of the broken DNA (B) Signup and view all the answers

What is the outcome of the resolution of the double Holliday junction?

Generation of new genetic combinations (C) Signup and view all the answers

What is the primary function of RecA protein in homologous recombination?

To bind to the 3’ overhangs and form a protein-DNA filament (A) Signup and view all the answers

What is the outcome of the activation of the extrinsic pathway of apoptosis?

The controlled death of the cell (B) Signup and view all the answers

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 (B) Signup and view all the answers

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 (B) Signup and view all the answers

What is the key difference between the extrinsic and intrinsic pathways of apoptosis?

The type of signal that activates the pathway (B) Signup and view all the answers

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 (D) Signup and view all the answers

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 (B) Signup and view all the answers