أسئلة الجينتكس السابعة (قبل التعديل)
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Questions and Answers

How many sense codons code for amino acids?

  • 3
  • 64
  • 61 (correct)
  • 20

Which of the following is a termination codon?

  • AUC
  • AUG
  • UAA (correct)
  • CUG

What role does AUG serve in the process of translation?

  • It has no function.
  • It initiates protein synthesis. (correct)
  • It encodes for a termination signal.
  • It encodes for an amino acid other than methionine.

How many non-sense codons are there in the genetic code?

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

If there are 64 total codons, what is the maximum number of unique amino acids that can be coded for?

<p>20 (D)</p> Signup and view all the answers

What term describes an amino acid that is attached to its specific tRNA?

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

What type of bond forms between an amino acid and its specific tRNA during activation?

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

Which type of enzyme is specifically involved in the synthesis of proteins by catalyzing the attachment of amino acids to their respective tRNA?

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

What is the first step required before an amino acid can participate in protein synthesis?

<p>Activation of amino acids (D)</p> Signup and view all the answers

What is the main source of energy required for the process of protein synthesis?

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

Which of the following statements is true regarding tRNA?

<p>tRNA carries activated amino acids only. (B)</p> Signup and view all the answers

During the activation of amino acids, what is primarily being synthesized?

<p>Aminoacyl-tRNA (A)</p> Signup and view all the answers

Which factor is primarily responsible for promoting the elongation phase of protein synthesis?

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

What role do releasing factors play in the process of protein synthesis?

<p>Terminate the protein synthesis (B)</p> Signup and view all the answers

Which of the following is NOT a type of protein factor involved in protein synthesis?

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

What causes the termination of polypeptide chain elongation during translation?

<p>Encountering a non-sense codon (C)</p> Signup and view all the answers

Which of the following codons are classified as non-sense codons?

<p>UAA, UAG, UGA (D)</p> Signup and view all the answers

What happens to the A site of the ribosome when a non-sense codon is presented during translation?

<p>It becomes free for other tRNAs to bind. (B)</p> Signup and view all the answers

Which statement correctly describes the role of non-sense codons in the translation process?

<p>They act as stop signals for translation. (D)</p> Signup and view all the answers

During translation, what occurs immediately after encountering a non-sense codon?

<p>Termination factors are recruited to facilitate release. (C)</p> Signup and view all the answers

How many high energy phosphate bonds are cleaved for the formation of one peptide bond?

<p>4 (A)</p> Signup and view all the answers

Which two types of energy sources are primarily used in the formation of a peptide bond?

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

What role does GTP play in the process of peptide bond formation?

<p>It assists in the binding of aminoacyl-tRNA and translocation. (B)</p> Signup and view all the answers

How many ATP molecules are directly involved in the activation of amino acids for peptide bond formation?

<p>1 (D)</p> Signup and view all the answers

What is the total number of GTP molecules cleaved during the formation of one peptide bond?

<p>1 (C)</p> Signup and view all the answers

What is the primary function of mRNA in the process of protein synthesis?

<p>To carry the genetic instructions from DNA to the ribosome (C)</p> Signup and view all the answers

Which component is primarily responsible for linking amino acids to their corresponding tRNA?

<p>Aminoacyl-tRNA (A)</p> Signup and view all the answers

How are amino acids classified in the context of protein synthesis?

<p>They are the building blocks of proteins (B)</p> Signup and view all the answers

What is the role of tRNA in protein synthesis?

<p>To transfer amino acids to the ribosome (A)</p> Signup and view all the answers

In the protein synthesis process, what do the amino acids bind to before being incorporated into a protein?

<p>Aminoacyl-tRNA (B)</p> Signup and view all the answers

How many high energy phosphate bonds are cleaved in total when forming one peptide bond?

<p>4 (A)</p> Signup and view all the answers

Which energy source is NOT utilized during the formation of one peptide bond?

<p>2 ATP (B)</p> Signup and view all the answers

What is the total number of GTP molecules cleaved specifically for the binding and translocation during peptide bond formation?

<p>2 (D)</p> Signup and view all the answers

Which process involves the cleavage of high energy bonds for peptide bond formation?

<p>Activation of amino acids (A)</p> Signup and view all the answers

For the activation of amino acids in peptide bond formation, which of the following statements is true?

<p>It cleaves 2 high energy phosphate bonds from 1 ATP. (A)</p> Signup and view all the answers

What is formed when prokaryotic 50S and 30S ribosomal subunits combine?

<p>70S ribosome (C)</p> Signup and view all the answers

Which statement is true regarding the ribosomal subunits involved in prokaryotic translation?

<p>The 50S and 30S subunits combine to form a 70S ribosome. (D)</p> Signup and view all the answers

Which component of the ribosome is responsible for catalyzing peptide bond formation?

<p>peptidyl transferase enzyme (A)</p> Signup and view all the answers

What is the primary movement of the ribosome after the formation of a peptide bond?

<p>It moves 3 nucleotides towards the 3' end of mRNA. (D)</p> Signup and view all the answers

What distinguishes the 70S ribosome from the 80S ribosome?

<p>The 70S ribosome is smaller than the 80S ribosome. (C)</p> Signup and view all the answers

Which ribosomal subunit contains the peptidyl transferase enzyme responsible for peptide bond formation?

<p>60S subunit (A)</p> Signup and view all the answers

Which of the following is a characteristic of prokaryotic ribosomes?

<p>They consist of 50S and 30S subunits. (A)</p> Signup and view all the answers

How do prokaryotic ribosomes facilitate protein synthesis?

<p>By forming the 70S ribosome from 50S and 30S subunits. (C)</p> Signup and view all the answers

What process follows peptide bond formation during translation?

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

Which of the following statements about ribosomal movement during translation is accurate?

<p>The ribosome moves 3 nucleotides towards the 3' end of mRNA post peptide bond formation. (C)</p> Signup and view all the answers

What is the primary advantage of forming a polyribosome during translation?

<p>It facilitates the production of multiple polypeptides from a single mRNA strand. (B)</p> Signup and view all the answers

How do polysomes affect the efficiency of protein synthesis?

<p>They contribute to faster production of proteins by utilizing multiple ribosomes. (B)</p> Signup and view all the answers

What is the structural feature of polysomes?

<p>Multiple ribosomes translating a single mRNA. (A)</p> Signup and view all the answers

What is produced as a result of a polyribosome translating a single mRNA?

<p>Multiple distinct polypeptides varying in length and composition. (C)</p> Signup and view all the answers

Which statement accurately describes the relationship between mRNA and polyribosomes?

<p>Polyribosomes can translate mRNA into several different polypeptides simultaneously. (A)</p> Signup and view all the answers

Study Notes

Codons

  • There are 64 codons.
  • 61 codons code for 20 amino acids.
  • 3 codons are non-sense codons or termination codons (UAA, UAG, UGA).

Initiation Codon

  • AUG codes for methionine and acts as the initiation codon for translation.

Translation Process

  • Translation requires initiation, elongation and termination steps.
  • Initiation: Involves initiation factors (IF).
  • Elongation: Involves elongation factors (EF).
  • Termination: Involves releasing factors (RF).
  • Energy Sources: ATP & GTP.

Activation of Amino Acids

  • Amino acids must be activated before translation.
  • Amino acids bind to specific tRNA molecules via an ester bond.
  • This process is called aminoacyl-tRNA synthesis.

Termination

  • Elongation continues until the A site is occupied by a non-sense codon (UAA, UAG, UGA).
  • This signals the termination of translation.

Energy Needs

  • Four high energy phosphate bonds are cleaved for each new peptide bond formed:
    • 2 ATP: Used for activation of amino acids.
    • 1 GTP: Used for binding aminoacyl-tRNA to the A site.
    • 1 GTP: Used for translocation.

Translation Overview

  • mRNA carries genetic information from DNA to the ribosome.
  • tRNA carries amino acids to the ribosome.
  • Amino acids are the building blocks of proteins.
  • Aminoacyl-tRNA synthetase connects specific amino acids to their corresponding tRNA molecules.

Ribosome Formation and Function

  • Prokaryotic ribosomes are composed of a 30S and a 50S subunit, which assemble to form a 70S ribosome.
  • The formation of a peptide bond is catalyzed by peptidyl transferase, an enzyme located within the 60S subunit.
  • Following the formation of a peptide bond, the ribosome moves three nucleotides along the mRNA towards the 3' end.

Energy Requirements

  • Four high-energy phosphate bonds are cleaved for each new peptide bond formed:
    • Two ATP molecules are required for amino acid activation.
    • One GTP molecule is used for the binding of aminoacyl-tRNA to the A site.
    • One GTP molecule is used for translocation.

Polyribosomes

  • Multiple ribosomes can translate a single mRNA molecule simultaneously, forming a polyribosome (or polysome).
  • This process allows for the production of many polypeptides from a single mRNA molecule, increasing protein synthesis efficiency.

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