Molecular Biology Quiz: Gene Function & Structure
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Questions and Answers

What is the primary function of telomeres in non-coding DNA sequences?

  • To code for proteins
  • To protect against chromosomal deterioration (correct)
  • To regulate RNA polymerase binding
  • To differentiate individuals

Which component of a gene is responsible for initiating transcription?

  • Terminator
  • Intron
  • Coding sequence
  • Promoter (correct)

During RNA processing, which non-coding regions are removed from the RNA transcript?

  • Exons
  • Introns (correct)
  • Telomeres
  • Promoters

In what direction does transcription occur?

<p>5' → 3' (C)</p> Signup and view all the answers

What role do gene regulatory sequences play in the transcription process?

<p>They regulate transcription by affecting RNA polymerase binding (B)</p> Signup and view all the answers

Which part of a gene signals the end of transcription?

<p>Terminator (C)</p> Signup and view all the answers

Which RNA molecule is involved in bringing amino acids to the ribosome during protein synthesis?

<p>tRNA (D)</p> Signup and view all the answers

What percentage of the human genome is made up of protein-coding genes?

<p>1.5% (B)</p> Signup and view all the answers

What process is crucial for the functionality of proteins like insulin?

<p>Post-translational modifications (C)</p> Signup and view all the answers

What is the primary role of ubiquitin in protein metabolism?

<p>Tagging proteins for degradation (C)</p> Signup and view all the answers

How do proteasomes contribute to cellular function?

<p>By degrading unneeded proteins (B)</p> Signup and view all the answers

What initiates the process of protein degradation by the proteasome?

<p>Ubiquitination (B)</p> Signup and view all the answers

Which component of the proteasome controls access to the proteolytic core?

<p>α-subunit gate (B)</p> Signup and view all the answers

What is the primary purpose of the 5'-end cap added during the capping process?

<p>To protect RNA from degradation (C)</p> Signup and view all the answers

Which post-transcriptional modification involves adding a poly-A tail to the RNA transcript?

<p>Polyadenylation (C)</p> Signup and view all the answers

What is a consequence of alternative splicing in eukaryotic cells?

<p>It allows the production of different protein variants from a single gene. (B)</p> Signup and view all the answers

Which of the following is NOT a major post-transcriptional event in eukaryotic cells?

<p>Ribosomal assembly (C)</p> Signup and view all the answers

Why do prokaryotes not undergo post-transcriptional modifications?

<p>They lack introns in their genes. (B)</p> Signup and view all the answers

What purpose does RNA splicing serve in the maturation of mRNA?

<p>It removes non-coding sequences from the RNA transcript. (A)</p> Signup and view all the answers

What role does polyadenylation play regarding RNA stability?

<p>It increases RNA stability. (B)</p> Signup and view all the answers

Which of the following statements accurately describes the chemical diversity of amino acids?

<p>The side chains of amino acids determine their chemical properties. (B)</p> Signup and view all the answers

What nucleotide sequence marks the starting point of translation?

<p>AUG (C)</p> Signup and view all the answers

Which site of the ribosome is where the tRNA carrying the growing peptide chain is located during elongation?

<p>P site (D)</p> Signup and view all the answers

During which phase of translation do release factors bind to the mRNA?

<p>Termination (B)</p> Signup and view all the answers

What is the primary structure of a protein dependent on?

<p>Covalent peptide bonds between adjacent amino acids (C)</p> Signup and view all the answers

What stabilizes the secondary structure of proteins, such as α-helices and β-pleated sheets?

<p>Hydrogen bonds between non-adjacent amino acids (B)</p> Signup and view all the answers

What happens to the tRNA in the P site after it has transferred its amino acid during elongation?

<p>It is deacylated and exits the ribosome (B)</p> Signup and view all the answers

Which phase of translation involves the ribosome moving along the mRNA?

<p>Translocation (A)</p> Signup and view all the answers

How does the primary structure influence the overall protein folding?

<p>By dictating R group interactions that affect folding (B)</p> Signup and view all the answers

What is the primary characteristic of the tertiary structure of proteins?

<p>It is the 3D shape determined by interactions between the R groups. (B)</p> Signup and view all the answers

Which type of bond is NOT involved in stabilizing the tertiary structure of proteins?

<p>Peptide bonds (A)</p> Signup and view all the answers

What defines the quaternary structure of a protein?

<p>The association of multiple polypeptide chains. (B)</p> Signup and view all the answers

Which description best fits globular proteins?

<p>Spherical and typically soluble in water. (B)</p> Signup and view all the answers

Which is a key feature of fibrous proteins?

<p>They provide strength and stability through a repetitive amino acid sequence. (A)</p> Signup and view all the answers

How is the specificity of an enzyme's active site determined?

<p>By the precise 3D shape of the tertiary structure. (A)</p> Signup and view all the answers

Which protein demonstrates a conjugated quaternary structure?

<p>Hemoglobin (B)</p> Signup and view all the answers

What role do hydrophobic interactions play in protein structure?

<p>They cause non-polar amino acids to avoid water. (D)</p> Signup and view all the answers

What is the main structural role of collagen in tissues?

<p>To provide mechanical strength and stability (B)</p> Signup and view all the answers

How do polar and non-polar amino acids affect protein folding?

<p>They influence the stability of the protein by affecting solubility (A)</p> Signup and view all the answers

What type of amino acids would likely be found on the surface of integral membrane proteins?

<p>Polar amino acids to form hydrophilic channels (B)</p> Signup and view all the answers

Which of the following is NOT a type of post-translational modification?

<p>Phase separation (D)</p> Signup and view all the answers

What is the effect of glycosylation on proteins?

<p>It influences protein stability and biological activity (B)</p> Signup and view all the answers

What happens to preproinsulin during its conversion to proinsulin?

<p>A disulfide bridge is formed between A and B chains (C)</p> Signup and view all the answers

Which type of protein is primarily involved in enzyme catalysis and hormonal regulation?

<p>Globular proteins (B)</p> Signup and view all the answers

How are disulfide bridges formed in proteins?

<p>By covalent bonding between cysteine residues (D)</p> Signup and view all the answers

Flashcards

Non-coding DNA

Regions in the genome not directly coding for proteins.

Gene structure

A gene consists of a promoter, coding sequence, and a terminator.

Promoter (gene)

Non-coding DNA sequence that starts transcription.

Coding sequence (gene)

Part of a gene that's transcribed into RNA.

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Terminator (gene)

Sequence signaling the end of transcription.

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Transcription direction

RNA polymerase adds nucleotides to the 3' end of mRNA.

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Transcription factors

Proteins that regulate gene expression by affecting RNA polymerase binding.

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Satellite DNA

Repetitive DNA sequences used for DNA profiling.

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Post-transcriptional modifications

Processes that modify RNA after transcription, affecting its structure and function, essential for producing mature mRNA in eukaryotes, but not in prokaryotes.

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RNA Capping

Adding a methyl group to the 5’ end of a newly transcribed RNA molecule. Protects from degradation and helps translation.

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Polyadenylation

Adding a poly-A tail (adenine nucleotides) to the 3’ end of RNA. Increases stability and nuclear export.

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RNA Splicing

Removing introns (non-coding regions) from RNA and joining exons (coding regions). Creates mature mRNA.

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Introns

Non-coding sequences in RNA that are removed during splicing.

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Exons

Coding sequences in RNA that remain after splicing to form the mature mRNA.

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Alternative Splicing

Producing multiple protein variants from a single gene by using different combinations of exons.

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Mature mRNA

Processed mRNA that has undergone capping, polyadenylation, and splicing, ready for translation into proteins.

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Initiation (translation)

The process where the ribosome assembles on the mRNA with the initiator tRNA, marking the start of protein synthesis.

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Elongation (translation)

The process of adding amino acids to the growing polypeptide chain, where tRNA molecules bring their specific amino acids to the ribosome.

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Translocation (translation)

The movement of the ribosome along the mRNA, shifting tRNAs and adding new amino acids to the polypeptide chain.

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Termination (translation)

The process where the ribosome encounters a stop codon, signaling the end of translation and the release of the completed protein.

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Primary Structure (1º)

The linear sequence of amino acids in a polypeptide chain, determined by the order of codons in the mRNA.

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Secondary Structure (2º)

The local folding of the polypeptide chain into repeating structural patterns like α-helices and β-pleated sheets, stabilized by hydrogen bonds.

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α-helix

A helical structure in the secondary structure of proteins, stabilized by hydrogen bonds between the backbone groups of the polypeptide chain.

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β-pleated sheet

A sheet-like structure in proteins, formed by hydrogen bonds between the backbone groups of the polypeptide chain.

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Tertiary Structure

The 3D shape of a protein formed by interactions between amino acid side chains (R groups).

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Quaternary Structure

The arrangement of multiple polypeptide chains in a protein, forming a complex structure. Some proteins also have additional non-protein components (e.g., heme in hemoglobin).

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What stabilizes Tertiary Structure?

Hydrogen bonds, ionic bonds, disulfide bridges (covalent bonds), and hydrophobic interactions all contribute to the stability of a protein's tertiary structure.

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Globular Protein

A spherical, water-soluble protein that typically has a biological function, like acting as an enzyme, hormone, or antibody.

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Fibrous Protein

A long, narrow, water-insoluble protein that provides structure and support, often found in connective tissues, bones, and skin.

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Insulin's Structure

Insulin is a globular protein with two polypeptide chains connected by disulfide bridges, making it water-soluble and allowing it to travel in the bloodstream.

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Why is Tertiary Structure Important?

A protein's function is directly related to its specific 3D shape. The tertiary structure creates active sites for enzymes, which allow them to bind to specific molecules.

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What affects Protein Solubility?

The arrangement of amino acids in a protein determines its solubility. Hydrophobic amino acids tend to cluster inside, while hydrophilic amino acids face outward towards water.

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Hydrophilic amino acids

Amino acids with polar side chains that attract water molecules. They tend to be found on the surface of proteins.

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Hydrophobic amino acids

Amino acids with non-polar side chains that repel water molecules. They often reside in the interior of proteins.

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Protein Folding

The process by which a polypeptide chain acquires a three-dimensional structure, determined by the sequence and interactions of its amino acids.

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Post-Translational Modifications

Chemical changes that occur to a protein after translation, influencing its function and stability.

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Disulfide Bridges

Covalent bonds formed between cysteine residues in a protein, stabilizing its structure.

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Proteolytic Cleavage

Removal of amino acids from a protein, often activating it or facilitating folding.

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Proteasome

A large protein complex that degrades damaged or unnecessary proteins. It breaks down proteins into amino acids, which can be recycled for new protein synthesis.

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Ubiquitin

A small protein that tags proteins for degradation. When a protein is tagged with ubiquitin, it signals to the proteasome to break it down.

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Proteasome Structure

The proteasome has two main parts: an outer regulatory complex that recognizes and accepts ubiquitinated proteins, and a central core that breaks down the proteins.

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Amino Acid Recycling

The proteasome breaks down unwanted proteins, releasing amino acids, which can then be used to build new proteins, making it a vital part of protein turnover.

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Study Notes

Non-Coding DNA Sequences

  • Non-coding DNA makes up most of the human genome (about 98.5%), not directly coding for proteins.
  • Satellite DNA (short tandem repeats) is used in DNA profiling to identify individuals.
  • Telomeres are repetitive sequences at chromosome ends, protecting against deterioration during replication.
  • Introns are non-coding regions within eukaryotic genes, removed during RNA processing.
  • Non-coding genes (e.g., tRNA, rRNA) produce functional RNA molecules that don't encode proteins.
  • Gene regulatory sequences (enhancers and silencers) control transcription by influencing RNA polymerase binding.

Gene Structure

  • A gene comprises three main sections: promoter, coding sequence, and terminator.

Promoter

  • The promoter is a non-coding DNA sequence upstream of a gene.
  • It acts as a binding site for RNA polymerase.
  • It is regulated by transcription factors to either activate or repress RNA polymerase binding.

Coding Sequence

  • The coding sequence is the part of the gene transcribed into RNA.
  • The RNA transcript is complementary to the DNA, except uracil (U) replaces thymine (T).

Terminator

  • The terminator sequence signals the end of transcription.
  • Transcription termination mechanisms differ between prokaryotes and eukaryotes.

Directionality of Transcription

  • Transcription proceeds in a 5' to 3' direction.
  • RNA polymerase adds RNA nucleotides to the 3' end of the growing mRNA strand.
  • Directionality depends on DNA orientation and RNA polymerase activity.

Post-Transcriptional Modifications in Eukaryotes

  • Eukaryotic cells modify their RNA after transcription.
  • Three major types of modifications include: capping, polyadenylation, and splicing.

Capping

  • Methylation occurs at the 5' end of the RNA transcript.
  • This protects the RNA from degradation and facilitates recognition by the translational machinery.

Polyadenylation

  • Addition of a poly-A tail (adenine nucleotides) to the 3' end of the RNA transcript.
  • Increases RNA stability and aids in RNA export.

Splicing

  • Removal of introns (non-coding sequences) and joining of exons (coding sequences) to form mature mRNA.
  • Alternative splicing allows for multiple protein variants to be produced from a single gene.

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Related Documents

Non-Coding DNA & Gene Structure - PDF

Description

Test your knowledge on the critical roles of non-coding DNA, transcription mechanisms, and RNA processing. This quiz covers essential concepts such as telomeres, gene regulatory sequences, and the nature of protein-coding genes in the human genome. Challenge yourself to understand the intricacies of molecular biology!

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