RNA Molecules and Protein Encoding
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Questions and Answers

What is the process of duplicating double-stranded DNA called?

  • Transcription
  • Gene Expression
  • Translation
  • Replication (correct)

What type of RNA molecule is a component of ribosomes?

  • Messenger RNA (mRNA)
  • Transfer RNA (tRNA)
  • Protein-encoding RNA
  • Ribosomal RNA (rRNA) (correct)

What is the process of copying the information encoded in DNA into RNA called?

  • Replication
  • Transcription (correct)
  • Protein Synthesis
  • Gene Expression

Why do cells require mechanisms to regulate gene expression?

<p>Because not all genes are needed at the same time or in equal quantities (D)</p> Signup and view all the answers

What is the result of regulating the synthesis of mRNA molecules?

<p>A rapid change in the levels of protein production (B)</p> Signup and view all the answers

What type of RNA molecule folds into a characteristic three-dimensional structure that plays a role in protein synthesis?

<p>All of the above (D)</p> Signup and view all the answers

What is the term for the process of reading the sequence of nucleotides in mRNA to build a chain of amino acids?

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

What is the primary function of ribosomes?

<p>To align and catalyze the formation of peptide bonds between amino acids (A)</p> Signup and view all the answers

How many different proteins can a cell's DNA encode?

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

What does a ribosome recognize on the mRNA molecule?

<p>The points at which protein synthesis should begin (B)</p> Signup and view all the answers

What is the result of a peptide bond formation between two amino acids?

<p>A polypeptide chain is formed (D)</p> Signup and view all the answers

What is the purpose of the ribosome binding site?

<p>To initiate protein synthesis (D)</p> Signup and view all the answers

What is the product of protein synthesis initiated by a ribosome?

<p>A polypeptide chain (C)</p> Signup and view all the answers

What do ribosomes string together to make a polypeptide?

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

Which of the following enzymes plays a crucial role in relieving the tension caused by unwinding the two strands of the DNA helix?

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

What is the primary function of helicases during DNA replication?

<p>To unwind the DNA helix at the replication fork (B)</p> Signup and view all the answers

What is the direction of DNA synthesis?

<p>59 to 39 (C)</p> Signup and view all the answers

What type of molecule lacks an initiating site and will not be replicated?

<p>DNA molecule without an origin of replication (D)</p> Signup and view all the answers

What is the function of primers in DNA replication?

<p>To provide short stretches of RNA complementary to the exposed templates (A)</p> Signup and view all the answers

Which of the following is NOT an enzyme involved in DNA replication?

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

What is the function of DNA ligase in DNA replication?

<p>To join two DNA fragments together (A)</p> Signup and view all the answers

Which type of chromosomes typically have multiple origin of replication sites?

<p>Archaeal and eukaryotic chromosomes (A)</p> Signup and view all the answers

What is the primary difference between prokaryotic and eukaryotic mRNA?

<p>Eukaryotic mRNA is synthesized in a precursor form, whereas prokaryotic mRNA is not (D)</p> Signup and view all the answers

What is the purpose of the poly A tail in eukaryotic mRNA?

<p>To stabilize the transcript and enhance translation (D)</p> Signup and view all the answers

What is the fate of the pre-mRNA in eukaryotic cells?

<p>It is processed to form mature mRNA (B)</p> Signup and view all the answers

What occurs at the 5' end of the pre-mRNA during processing?

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

Why is a deletion of two base pairs likely to have a greater consequence if it occurs in an exon rather than in an intron?

<p>Because exons code for amino acids, while introns do not (A)</p> Signup and view all the answers

What is the purpose of the cap at the 5' end of the pre-mRNA?

<p>To enhance translation and stabilize the transcript (B)</p> Signup and view all the answers

What is the characteristic of eukaryotic mRNA that distinguishes it from prokaryotic mRNA?

<p>Eukaryotic mRNA is monocistronic, while prokaryotic mRNA is polycistronic (A)</p> Signup and view all the answers

What is the result of polyadenylation during eukaryotic mRNA processing?

<p>The cleavage of the transcript at a specific sequence and the addition of adenine derivatives (B)</p> Signup and view all the answers

What is the importance of using the correct reading frame in protein synthesis?

<p>To prevent the formation of faulty proteins (A)</p> Signup and view all the answers

What is the function of the initiating tRNA in protein synthesis?

<p>To recognize the start codon AUG (C)</p> Signup and view all the answers

What is the consequence of not using the correct reading frame in protein synthesis?

<p>The formation of a faulty protein (B)</p> Signup and view all the answers

Which antibiotic interferes with the function of the bacterial 70S ribosome?

<p>All of the above (D)</p> Signup and view all the answers

What is the function of the tRNA that recognizes the mRNA codon CCG?

<p>To carry the amino acid proline (D)</p> Signup and view all the answers

What is the significance of the 'S' in the 30S and 50S subunits of the ribosome?

<p>It stands for 'Svedberg unit', a measure of size (C)</p> Signup and view all the answers

Which amino acid is carried by the initiating tRNA in protein synthesis?

<p>N-formylmethionine (f-Met) (D)</p> Signup and view all the answers

What is the role of the position of the first AUG codon in protein synthesis?

<p>It determines the reading frame used for translation (A)</p> Signup and view all the answers

What is the function of the tRNA molecule in protein synthesis?

<p>To carry a specific amino acid dictated by its anticodon (A)</p> Signup and view all the answers

What is the role of the 'start' codon in protein synthesis?

<p>To initiate translation (A)</p> Signup and view all the answers

What is the result of the sequence of nucleotides in the codon UUA?

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

What is the function of the codon UAA?

<p>To terminate translation (C)</p> Signup and view all the answers

What is the consequence of a mutation that changes the codon AUG to AUA?

<p>The sequence of amino acids will be altered (A)</p> Signup and view all the answers

What is the role of the codon table in protein synthesis?

<p>To correlate codons to amino acids (B)</p> Signup and view all the answers

In which direction does the ribosome move along the mRNA during protein synthesis?

<p>59 to 39 (C)</p> Signup and view all the answers

What does the ribosome present to the cell during protein synthesis?

<p>Each codon in a sequential order (C)</p> Signup and view all the answers

What is the result of the sequence of nucleotides in the codon GCU?

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

What is the importance of maintaining the correct reading frame during protein synthesis?

<p>To ensure that the correct amino acid is added to the polypeptide chain (D)</p> Signup and view all the answers

What is the function of the codon CCG in protein synthesis?

<p>To incorporate Proline into the protein (A)</p> Signup and view all the answers

What is the consequence of a mutation that changes the codon UGG to UGA?

<p>The termination of translation will be initiated (C)</p> Signup and view all the answers

What is the result of the ribosome moving along the mRNA during protein synthesis?

<p>A polypeptide chain is formed (C)</p> Signup and view all the answers

What is the role of the anticodon in tRNA?

<p>To pair with the codon on the mRNA (D)</p> Signup and view all the answers

What is the function of the codon in protein synthesis?

<p>To specify an amino acid or a 'stop' signal. (A)</p> Signup and view all the answers

What is the role of the ribosome during protein synthesis?

<p>To translate the genetic code from mRNA to a polypeptide chain (D)</p> Signup and view all the answers

What is the consequence of the ribosome not moving along the mRNA during protein synthesis?

<p>The polypeptide chain is formed incorrectly (C)</p> Signup and view all the answers

What is the result of a codon specifying more than one amino acid?

<p>Degeneracy in the genetic code. (A)</p> Signup and view all the answers

What is the consequence of a codon specifying a 'stop' signal?

<p>The ribosome releases the polypeptide chain. (A)</p> Signup and view all the answers

How many possible reading frames are there in a given sequence of nucleotides in mRNA?

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

What determines the beginning and end of the coding region in mRNA?

<p>The sequence of nucleotides. (C)</p> Signup and view all the answers

What is the significance of the ribosome-binding site?

<p>It is the site where the ribosome assembles and translation begins. (D)</p> Signup and view all the answers

In which direction does the ribosome move along the mRNA during translation?

<p>5' to 3' (A)</p> Signup and view all the answers

What is the consequence of not using the correct reading frame during protein synthesis?

<p>A non-functional protein is synthesized. (A)</p> Signup and view all the answers

Study Notes

Types of RNA Molecules

  • There are three functional types of RNA molecules: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
  • Each type of RNA is transcribed from different genes and plays a critical role in protein synthesis

RNA Function in Protein Synthesis

  • mRNA is translated into protein
  • tRNA and rRNA fold into characteristic three-dimensional structures that each play a role in protein synthesis
  • Ribosomal RNA is a component of ribosomes, which are the site of protein synthesis

Regulation of Gene Expression

  • Cells can regulate gene expression by controlling the synthesis of mRNA molecules
  • Regulating gene expression allows cells to quickly change the levels of protein production

Replication and Transcription

  • Replication is the process of duplicating double-stranded DNA
  • Transcription is the process of copying the information encoded in DNA into RNA
  • DNA gyrase and helicases are enzymes that temporarily break and unwind the DNA helix at the origin of replication
  • Primases synthesize short stretches of RNA complementary to the exposed templates

Ribosomes and Translation

  • Ribosomes are translation "machines" that string amino acids together to make a polypeptide
  • Ribosomes locate key punctuation sequences on the mRNA molecule, such as the start codon
  • The correct reading frame is crucial for protein synthesis

Transfer RNA (tRNA)

  • tRNA carries amino acids and recognizes mRNA codons
  • The anticodon of tRNA dictates the amino acid it carries

Prokaryotic and Eukaryotic Ribosomes

  • Prokaryotic ribosomes are composed of a 30S subunit and a 50S subunit
  • Eukaryotic ribosomes differ significantly from prokaryotic ribosomes in several aspects of transcription and translation

Eukaryotic mRNA Processing

  • Eukaryotic mRNA is synthesized in a precursor form, called pre-mRNA
  • Pre-mRNA must be processed (altered) during and after transcription to form mature mRNA
  • Processing involves capping, polyadenylation, and splicing

Intron and Exon

  • An intron is a segment of DNA that is removed during processing to form mature mRNA
  • A deletion of two base pairs would have a greater consequence if it occurred in an exon rather than in an intron

Translation Initiation and Termination

  • Start codon: AUG, typically the first codon after a ribosome-binding site, initiates translation
  • Stop codon: three codons (UAA, UAG, UGA) that terminate translation, signaling the end of the protein

The Genetic Code

  • Correlates a codon (series of three nucleotides) to an amino acid
  • Many amino acids are specified by more than one codon
  • Example: threonine is specified by four codons (ACU, ACC, ACA, ACG) that differ only in the third nucleotide

Codon Table

  • First letter: U, C, A, G
  • Second letter: U, C, A, G
  • Third letter: U, C, A, G
  • Corresponding amino acids:
    • UUU: Phe (phenylalanine)
    • UCU: Ser (serine)
    • UAU: Tyr (tyrosine)
    • UGU: Cys (cysteine)
    • ...and so on

Reading Frames

  • Translation begins at the start codon and ends at the stop codon
  • Any given sequence has three possible reading frames, or ways in which triplets can be grouped
  • If translation begins in the wrong reading frame, a very different, and generally non-functional, protein is synthesized

Ribosome Movement

  • The ribosome moves along the mRNA in the 5' to 3' direction
  • Presents each codon in a sequential order for decoding while maintaining the correct reading frame

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Description

This quiz covers the three functional types of RNA molecules, including messenger RNA, ribosomal RNA, and transfer RNA, and their roles in protein encoding and transcription.

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