DNA TRANSLATION

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Questions and Answers

What is the primary function of hemoglobin and myoglobin?

Regulation of cell division

Transport of oxygen (correct)

Defense against pathogens

Structural support in cells

Which protein type is primarily responsible for muscle contraction?

Histones

Tubulin

Immunoglobulins

Actin and Myosin (correct)

What role do transcription factors play in cellular function?

Regulate gene expression (correct)

Regulate the transport of molecules across membranes

Provide structural integrity to cells

Bind to DNA to initiate replication

Which of the following protein types is associated with the immune system of vertebrates?

Immunoglobulins (Antibodies) (D) Signup and view all the answers

What is the main function of enzymes in biological systems?

Catalyze biochemical reactions (A) Signup and view all the answers

What occurs during the formation of a peptide bond between two amino acids?

A dehydration reaction between an amino group and a carboxyl group (D) Signup and view all the answers

Which property can vary among the R groups (side chains) of amino acids?

Polarity, including hydrophobic and hydrophilic characteristics (B) Signup and view all the answers

What distinguishes the N-terminus from the C-terminus in a polypeptide chain?

The N-terminus has a free amino group, while the C-terminus has a free carboxyl group (B) Signup and view all the answers

Which of the following amino acids is a modification of lysine?

Pyrrolysine (B) Signup and view all the answers

What is a common feature of all 20 amino acids found in proteins?

All contain a central carbon atom bonded to an amino group, carboxyl group, and an R group (D) Signup and view all the answers

What is the importance of the reading frame in the translation process?

It ensures codons are grouped correctly for polypeptide production. (B) Signup and view all the answers

Which statement best describes codons?

Codons specify a single amino acid and are read in groups of three nucleotides. (B) Signup and view all the answers

How does the universality of the genetic code impact genetic engineering?

It allows for the consistent expression of transplanted genes across species. (A) Signup and view all the answers

What defines the non-overlapping nature of codons?

Each nucleotide participates in only one codon. (C) Signup and view all the answers

Why is the triplet code significant in the genetic code?

It provides a direct linkage between nucleotides and amino acids. (A) Signup and view all the answers

How many amino acid codons are present in the genetic code?

61 (C) Signup and view all the answers

What does a stop codon signal during the process of translation?

To end translation (B) Signup and view all the answers

Which of the following statements is true regarding genetic codons?

A single amino acid may be specified by more than one codon. (D) Signup and view all the answers

Which codon serves as the start signal in protein synthesis?

AUG (D) Signup and view all the answers

What is the total number of stop codons in the genetic code?

3 (D) Signup and view all the answers

What characteristic of the genetic code allows multiple codons to specify the same amino acid?

Codon redundancy (A) Signup and view all the answers

Which of the following statements about stop codons is correct?

Stop codons terminate the process of translation. (B) Signup and view all the answers

How many total genetic codons are there and what are their classifications?

64 genetic codons, including stop and start codons. (C) Signup and view all the answers

Which amino acid is coded by the start codon AUG?

Methionine (D) Signup and view all the answers

What is true about the relationship between codons and amino acids?

Codons are redundant, allowing for multiple codons for the same amino acid. (C) Signup and view all the answers

What is a silent mutation?

A base change that does not alter the amino acid specified. (C) Signup and view all the answers

Which type of mutation results in a nonfunctional protein?

Nonsense mutation (D) Signup and view all the answers

What is true about a missense mutation?

It changes the specified amino acid to a different one. (A) Signup and view all the answers

Which of the following best describes point mutations?

Single base changes that can affect protein synthesis. (D) Signup and view all the answers

Which type of mutation maintains the original amino acid specified?

Silent mutation (B) Signup and view all the answers

What effect do frameshift mutations have on proteins?

They change the entire reading frame and amino acid sequence. (B) Signup and view all the answers

What is the primary consequence of InDel mutations?

They may change the reading frame and amino acid sequence. (C) Signup and view all the answers

Which of the following best describes an insertion mutation?

It adds nucleotide pairs to a gene. (A) Signup and view all the answers

What is the impact of deletion mutations on a gene?

They may disrupt the reading frame and change the resulting protein. (B) Signup and view all the answers

Why are frameshift mutations considered disastrous for proteins?

They lead to entirely different amino acid sequences from the mutation point. (B) Signup and view all the answers

What are the requirements for the translation process?

Amino acids, mRNA, tRNA, ribosomes, enzymes (C) Signup and view all the answers

Which phase of translation involves the addition of amino acids to the growing polypeptide chain?

Elongation (C) Signup and view all the answers

What is the main function of transfer RNA (tRNA) in translation?

To carry amino acids to the ribosome (D) Signup and view all the answers

Which of the following best describes the termination stage in translation?

The ribosome releases the completed polypeptide (D) Signup and view all the answers

What is the role of ribosomes in the translation process?

To hold mRNA and facilitate the assembly of amino acids (D) Signup and view all the answers

What is the structure of tRNA known as?

Cloverleaf structure (B) Signup and view all the answers

In tRNA, the amino acid is linked to which sequence?

CCA sequence (A) Signup and view all the answers

What ensures the proper pairing of the tRNA anticodon with mRNA codons?

Hydrogen bonds (D) Signup and view all the answers

What is the role of the anticodon in tRNA?

It ensures proper codon-anticodon pairing. (B) Signup and view all the answers

What is the general length of tRNA molecules?

75–90 nucleotides (B) Signup and view all the answers

What is the process called that chemically links an amino acid to tRNA?

Aminoacylation (C) Signup and view all the answers

What enzyme is responsible for catalyzing the aminoacylation of tRNA?

Aminoacyl tRNA synthetase (A) Signup and view all the answers

Which part of the tRNA is the amino acid linked to during aminoacylation?

CCA sequence at the 3′ end (B) Signup and view all the answers

How specific are aminoacyl tRNA synthetases in terms of amino acid recognition?

They recognize only one amino acid (A) Signup and view all the answers

What is the significance of the CCA sequence at the 3′ end of tRNA?

It is where the amino acid is covalently linked (C) Signup and view all the answers

Which of the following statements about the third mRNA codon base is true?

It forms a loose wobble pair with the first tRNA anticodon base. (C) Signup and view all the answers

What role does inosine play in the wobble hypothesis?

Serves as a modified base in tRNA to form wobble pairs. (B) Signup and view all the answers

How does the initial two ribonucleotides of mRNA codons compare to the third ribonucleotide?

They are more critical for determining the amino acid. (C) Signup and view all the answers

Which aspect of the wobble hypothesis is most significant?

The ability of the third base to pair loosely. (C) Signup and view all the answers

What is the primary function of the wobble pairing mechanism in translation?

To allow multiple codons to code for the same amino acid. (B) Signup and view all the answers

What are the components of eukaryotic ribosomes?

80S and 60S subunits (C) Signup and view all the answers

In the process of translation, what site is responsible for tRNA exit?

E site (D) Signup and view all the answers

What is the correct order of the movement of tRNAs during translation?

A -> P -> E (B) Signup and view all the answers

Which of the following statements about prokaryotic ribosomes is true?

They are 70S, consisting of 50S and 30S subunits. (A) Signup and view all the answers

Which ribosomal site is primarily involved in forming peptide bonds?

P site (B) Signup and view all the answers

What is the role of Initiation Factor 1 (IF1) during the initiation of translation in bacteria?

It prevents premature entry of tRNA to the A site. (B) Signup and view all the answers

What is the function of the Shine-Dalgarno sequence in bacterial mRNA?

It ensures proper binding of mRNA to the 30S subunit. (C) Signup and view all the answers

Which factor is directly responsible for the binding of fMet-tRNA to the 30S subunit?

IF2-GTP (B) Signup and view all the answers

What sequence precedes the AUG start codon in bacterial mRNA?

AGGAGGU (A) Signup and view all the answers

What happens to the initiation factors after the initiation complex is formed?

They are released from the ribosome. (B) Signup and view all the answers

What type of tRNA enters the P site in prokaryotes during initiation of translation?

fMet-tRNA (B) Signup and view all the answers

Which ribosomal RNA functions as a ribozyme for peptide bond formation in eukaryotes?

28S rRNA (D) Signup and view all the answers

Which of the following correctly describes the movement of tRNA during the elongation phase of translation?

tRNA in the P site moves to E site and the elongating chain shifts to tRNA in A site. (B) Signup and view all the answers

What is the role of the peptidyl transferase in ribosomes?

It joins amino acids by catalyzing peptide bond formation. (D) Signup and view all the answers

How does the process of translation directionality occur?

Translation occurs in the 5’ to 3’ direction. (D) Signup and view all the answers

Which eukaryotic initiation factor is responsible for helping Met-tRNA bind to the AUG codon of mRNA?

eIF2 (C) Signup and view all the answers

What role does the Kozak sequence play in translation initiation in eukaryotes?

It binds to the 40S ribosomal subunit. (B) Signup and view all the answers

In the initiation complex, what occurs after the Met-tRNA binds to the AUG codon?

The 60S subunit combines with the 40S subunit. (D) Signup and view all the answers

Which ribosomal RNA is involved in the binding of the Kozak sequence during translation initiation?

18S rRNA (D) Signup and view all the answers

Which of the following statements is true regarding the initiation complex in eukaryotes?

Multiple initiation factors are required to form the complex. (D) Signup and view all the answers

What signals the termination of translation?

Stop codons (A) Signup and view all the answers

What role do GTP-dependent release factors play in translation termination?

They stimulate hydrolysis of polypeptide from peptidyl tRNA (B) Signup and view all the answers

Which statement is true regarding stop codons?

They do not specify any amino acid (B) Signup and view all the answers

What happens to the polypeptide during translation termination?

It is released from the translation complex (B) Signup and view all the answers

How many stop codons are involved in the termination of translation?

Three (C) Signup and view all the answers

What do polyribosomes indicate in a cell?

Active protein synthesis (A) Signup and view all the answers

How does mRNA interact with ribosomes during translation?

It can associate with multiple small subunits at once. (D) Signup and view all the answers

What is the structural significance of polyribosomes?

They demonstrate multiple ribosomes translating the same mRNA. (D) Signup and view all the answers

What happens to mRNA as it is being translated by ribosomes?

It can continue to engage with additional ribosomal complexes. (B) Signup and view all the answers

Which statement is true regarding polyribosomes?

They are involved in the rapid synthesis of proteins. (D) Signup and view all the answers

What is a common type of modification that occurs to individual amino acid residues?

Phosphorylation (A) Signup and view all the answers

Which statement accurately describes one of the posttranslational modifications of proteins?

Carbohydrate side chains are sometimes attached to proteins. (B) Signup and view all the answers

What happens to the N-terminus during posttranslational modifications?

It can be modified or removed. (C) Signup and view all the answers

How may polypeptide chains be altered during posttranslational modifications?

By being trimmed (B) Signup and view all the answers

What role do metal complexes play in posttranslational modifications?

They stabilize the protein structure. (B) Signup and view all the answers

Study Notes

Protein Functions

Hemoglobin and Myoglobin: Transport oxygen crucial for cellular metabolism.
Collagen and Keratin: Structural proteins supporting skin, connective tissue, and hair.
Actin and Myosin: Contractile proteins in muscle tissue.
Tubulin: Forms microtubules, vital for mitotic and meiotic spindle fibers.
Immunoglobulins (Antibodies): Play a role in vertebrate immune systems.
Transport Proteins: Facilitate molecule movement across membranes.
Hormones and Receptors: Control various chemical activities through interaction.
Histones: Bind to DNA in eukaryotic cells.
Transcription Factors: Regulate gene expression.
Enzymes: Diverse and extensive protein group, catalyzing reactions.

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Description

This quiz explores the diverse functions of proteins in biological systems, including their roles in oxygen transport, structural support, muscle contraction, and immune response. It also covers enzymes, hormones, and gene regulation. Test your knowledge on how these vital molecules contribute to life processes.