Molecular Biology - Protein Synthesis Quiz

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Questions and Answers

What is the role of the release factor during termination of translation?

It assists in the assembly of the ribosomal subunits.

It synthesizes mRNA from the DNA template.

It hydrolyzes the bond between the last tRNA and the polypeptide. (correct)

It brings a new amino acid to the ribosome.

During transcription, what occurs in the nucleus?

RNA is replicated from RNA.

DNA serves as a template for mRNA. (correct)

Polypeptides are assembled from amino acids.

Ribosomal RNA is translated into messenger RNA.

What occurs after mRNA is processed in the nucleus?

mRNA is translated directly into a protein.

mRNA leaves the nucleus and enters the ribosome for translation. (correct)

mRNA is converted back into DNA for replication.

mRNA is degraded before it can leave the nucleus.

Which of the following represents the correct order of events in protein synthesis?

Replication, transcription, translation. Signup and view all the answers

What happens when the ribosome encounters a stop codon during translation?

The ribosome halts translation and releases the newly formed polypeptide. Signup and view all the answers

What must genetic material be able to do to fulfill its role in heredity?

Store information related to development, structure, and metabolic activity Signup and view all the answers

Which nucleic acid is associated with the genetic code?

Both DNA and RNA Signup and view all the answers

During the transformation of bacteria, what did Griffith conclude was responsible for the change in phenotype of the R strain?

A change in the genotype due to a substance from the S strain Signup and view all the answers

What is the primary role of RNA in relation to DNA?

To serve as a template for protein synthesis Signup and view all the answers

Which experimental condition led to the discovery of transformation in Griffith's experiment?

Combining heat-killed S strain with live R strain Signup and view all the answers

Which statement correctly differentiates DNA from protein regarding genetic material?

DNA is made from nucleotides, while proteins are made from amino acids Signup and view all the answers

What characteristic of genetic material allows for variability within a population?

The ability to undergo mutations Signup and view all the answers

Which component of the chromosome is primarily responsible for heredity?

DNA Signup and view all the answers

What is the direction in which the new DNA strand is synthesized during prokaryotic replication?

5'-3' Signup and view all the answers

Which of the following statements accurately describes telomeres?

Telomeres shorten with each cell division due to replication. Signup and view all the answers

What hypothesis did Beadle and Tatum propose in 1940 regarding genes and enzymes?

One gene-one enzyme hypothesis. Signup and view all the answers

What is a potential outcome of an error during DNA replication?

Mutations can serve as material for evolutionary processes. Signup and view all the answers

In eukaryotic replication, how many origins of replication are generally involved?

Numerous origins of replication Signup and view all the answers

Which of the following accurately represents a characteristic of DNA polymerase during replication?

It makes one mistake per 100,000 base pairs. Signup and view all the answers

Which process describes the synthesis of RNA from a DNA template?

Transcription Signup and view all the answers

What structural change occurs in hemoglobin in sickle cell anemia due to genetic mutation?

Defective β chain structure Signup and view all the answers

What is the primary function of DNA repair enzymes?

To correct errors in the DNA sequence Signup and view all the answers

What are replication bubbles associated with in eukaryotic DNA replication?

Multiple origins of replication Signup and view all the answers

What process allows introns to contribute to the production of different mRNAs from a single segment of DNA?

Alternative mRNA splicing Signup and view all the answers

Which statement accurately describes a property of the genetic code?

The code is universal among all organisms. Signup and view all the answers

During translation, where does the binding of tRNA with its corresponding amino acid occur?

At the ribosomes Signup and view all the answers

In what structure is ribosomal RNA (rRNA) produced?

Nucleolus Signup and view all the answers

What is the main function of aminoacyl-tRNA synthetases?

To attach amino acids to tRNA Signup and view all the answers

Which of the following statements about exons is correct?

Exons remain in the mRNA after splicing. Signup and view all the answers

What does the 'wobble' hypothesis predict about the third position of the tRNA anticodon?

It can vary and does not always follow standard pairing rules. Signup and view all the answers

What occurs when the polypeptide chain is fully formed during translation?

The ribosome dissociates into two subunits. Signup and view all the answers

How many types of tRNA molecules exist to correspond with the 20 amino acids in proteins?

45 Signup and view all the answers

What is one proposed function of introns in the genome?

They may allow for exon shuffling during meiosis. Signup and view all the answers

What defines the start of a gene and the direction of transcription?

Promoter Signup and view all the answers

Which type of RNA carries the genetic message from DNA to ribosomes?

Messenger RNA (mRNA) Signup and view all the answers

During transcription, RNA polymerase reads the DNA template in which direction?

3’ to 5’ direction Signup and view all the answers

Which of the following statements is true about the structure of RNA?

RNA has a ribose sugar. Signup and view all the answers

Which of the following components does NOT participate in the process of translation?

RNA polymerase Signup and view all the answers

What is the correct sequence of events in gene expression?

Transcription → Translation Signup and view all the answers

What role does tRNA play in the process of translation?

It transports amino acids to the ribosome. Signup and view all the answers

What does the one gene-one polypeptide hypothesis suggest?

Each gene codes for a single polypeptide chain. Signup and view all the answers

Which statement about the association of DNA and RNA during transcription is correct?

DNA-RNA association is temporary. Signup and view all the answers

Which of the following amino acids is encoded by the second codon mentioned?

Aspartate Signup and view all the answers

Study Notes

Biology Chapter 12: Molecular Biology of the Gene

Chapter Overview: This chapter details the molecular biology of the gene, encompassing the genetic material, DNA replication, gene expression (transcription and translation), and the accuracy of replication. It explores historical experiments and the fundamental mechanisms underlying genetic information flow.

12.1 The Genetic Material

Genetic Material Requirements: Genetic material must store developmental, structural, and metabolic information, be accurately replicated, be transmittable between generations, and allow for mutations creating genetic variability.
Nucleic Acids Discovery: Scientists identified deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) as major components within the nucleus.

12.2 Replication of DNA

DNA Replication: The process of copying a DNA molecule.
Semiconservative Replication: Each new DNA molecule contains one old strand and one newly synthesized strand.
Meselson-Stahl Experiment: Demonstrated the semiconservative nature of DNA replication using isotopes. This experiment provided evidence showing the parent strands act as a template for building new strands.

Steps of DNA Replication

Unwinding: Helicase unwinds the DNA double helix at the origin of replication. SSB proteins stabilize the open strands.
Complementary Base Pairing: Primase adds an RNA primer where DNA polymerase can bind. Complementary nucleotides are added and paired by DNA polymerase. DNA polymerase has a proofreading capability to avoid mistakes.
Joining: Ligase joins the Okazaki fragments, forming new strands.

Prokaryotic vs. Eukaryotic Replication

Prokaryotic Replication: Occurs in two directions from a single origin of replication within a circular loop in bacteria.
Eukaryotic Replication: Begins at numerous origins of replication forming replication bubbles, with replication forks moving outward in two directions.

12.3 Gene Expression: RNA & the Genetic Code

One Gene-One Enzyme Hypothesis: Proposed that a gene codes for a single enzyme.
Pauling's Sickle Cell Anemia Discovery: Suggested that a mutation in a gene could lead to a change in protein structure.

RNA Types

mRNA (messenger RNA): Carries the genetic message from DNA in the nucleus to ribosomes in the cytoplasm.
rRNA (ribosomal RNA): With proteins, forms ribosomes where polypeptide synthesis occurs
tRNA (transfer RNA): Transfers the appropriate amino acid to the ribosomes for protein synthesis.

The Central Dogma of Molecular Biology

Flow of Genetic Information: DNA → mRNA → Protein
Transcription: Production of mRNA from a DNA template within the nucleus.
Translation: Synthesis of proteins from an mRNA template at ribosomes in the cytoplasm.

12.4 Gene Expression: Transcription

RNA polymerase: Attaches to a promoter region, which signals the start of a gene, and initiates transcription.
mRNA synthesis: mRNA is formed based on the DNA template (with uracil replacing thymine), reading the DNA in a 3' to 5' direction.
Transcription termination: RNA polymerase stops when it reaches a termination sequence in the DNA.
mRNA processing: Primary mRNA transcripts in eukaryotes are modified before leaving the nucleus to mature mRNA:
- 5' cap: added to the 5' end, aiding ribosome binding
- poly-A tail: added to the 3' end, stabilizing the transcript
- splicing: removal of introns (non-coding regions) and joining of exons (coding regions).
Spliceosomes: Complex molecules involved in removing introns and joining exons during mRNA processing.
snRNA: Small nuclear RNAs are components of spliceosomes.

12.5 Gene Expression: Translation

tRNA: Transfers amino acids to the ribosomes according to the mRNA codons. Carries a specific amino acid and contains an anticodon to match to the mRNA codon.
Ribosomes: Cellular structures where amino acids are linked together to form polypeptide chains. Contains tRNA binding sites (A, P, E sites).
Translation steps:
- Initiation: Start codon (AUG) recognized. Initiator tRNA is bound to the start codon. Small and large ribosomal subunits assemble.
- Elongation: tRNA carrying amino acids bind to codons. Peptide bonds form between amino acids. Ribosome moves along mRNA.
- Termination: Stop codon encountered. Release factor binds. Polypeptide chain released. Ribosomal subunits dissociate.
Protein Folding: Polypeptide chain folds into its functional 3D structure assisted by chaperone proteins.

Accuracy of Replication

DNA Polymerase Accuracy: DNA polymerase is quite precise, often making one error for every 100,000 base pairs. Polymerases have proofreading capabilities.
Genetic Mutations: Permanent changes in the DNA sequence, which can arise from DNA replication errors or DNA damage. DNA repair enzymes can fix some of these errors.

12.6 Gene Expression: Summary

Genome Properties: Degenerative, unambiguous, and universal in the genetic code. The codons that code for an amino acid could be more than one.
Prokaryotic vs. Eukaryotic Gene Processing: Prokaryotes lack a nucleus. Their transcription and translation can occur concurrently. Eukaryotes have a nucleus in which transcription is isolated from the cytoplasm during which translation happens.

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Description

Test your knowledge on key concepts in molecular biology, particularly focusing on protein synthesis and the roles of various nucleic acids. This quiz will cover topics such as translation termination, transcription processes, and the significance of genetic material in heredity. Prepare to delve into the fascinating world of genetics with challenging questions!