Gene Expression and Transcription Quiz

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Questions and Answers

Which enzyme transcribes all eukaryotic tRNA genes?

RNA polymerase II

RNA polymerase I

RNA polymerase III (correct)

RNA polymerase IV

What is the first step in the initiation phase of protein biosynthesis?

tRNA charging

Formation of the 43 S pre initiation complex

Ribosomal dissociation (correct)

Binding of eukaryotic initiation factors

What is one of the significant processes required for converting pre-tRNA into mature tRNA?

Splicing of exons

Transcription initiation

Folding and base pairing (correct)

Addition of a 5' cap

Which nucleotide sequence codes for Methionine (Met) during protein synthesis?

AUG Signup and view all the answers

What is added to the 3' end of pre-tRNA during processing?

A CCA sequence Signup and view all the answers

What is the approximate size of eukaryotic ribosomal subunits combined?

80 S Signup and view all the answers

What is tRNA charging?

Recognition and attachment of specific amino acids to tRNA Signup and view all the answers

Which of the following statements about the flow of genetic information is correct?

Transcription occurs prior to translation. Signup and view all the answers

What is the function of eukaryotic initiation factors (elFs) in the initiation phase?

To facilitate ribosomal dissociation and bind to the 40 S subunit Signup and view all the answers

In the genetic code table, which first nucleotide results in multiple possible amino acids?

A Signup and view all the answers

What modification is NOT typically associated with eukaryotic pre-rRNA processing?

Addition of a Poly-A tail Signup and view all the answers

Which component plays an essential role in decoding mRNA during protein synthesis?

tRNA Signup and view all the answers

What is the correct order of the phases in protein biosynthesis?

Initiation, elongation, termination Signup and view all the answers

Which of the following is TRUE regarding the structure of codons?

Each codon is a triplet sequence of nucleotides. Signup and view all the answers

During the formation of the 43 S pre initiation complex, what binary complex forms before binding to the 40 S ribosomal subunit?

elF2 and GTP Signup and view all the answers

What is the role of ribosomes in protein synthesis?

To coordinate the interaction between tRNA, mRNA, and protein factors Signup and view all the answers

What is the first nucleotide added during RNA transcription?

A purine Signup and view all the answers

What role does the cap structure serve in mRNA?

It enhances ribosome binding for translation. Signup and view all the answers

What happens during the splicing process of mRNA?

Introns are removed and exons are ligated. Signup and view all the answers

What is the significance of the poly(A) tail on mRNA?

It aids in the transport of mRNA from the nucleus to the cytoplasm. Signup and view all the answers

Which of the following accurately describes the RNA polymerase function during elongation?

It moves along the DNA template strand in the 5' to 3' direction. Signup and view all the answers

Which characteristic of the cap added to mRNA is accurate?

It is composed of a tri-phosphate bridge. Signup and view all the answers

What does the term 'primary transcript' refer to in eukaryotic transcription?

The initial RNA sequence synthesized before processing. Signup and view all the answers

Which of the following statements about termination in transcription is true?

Termination depends on specific termination signals. Signup and view all the answers

Study Notes

Gene Expression

Gene expression is the process of protein synthesis, involving RNA transcription and translation.
A gene is a segment of DNA containing genetic information that codes for a polypeptide chain.
A genome is the total DNA content of a cell, equal to the total number of genes in a cell.

Transcription

Transcription is the synthesis of RNA from a DNA template by RNA polymerase enzymes.
Only one DNA strand (template strand) is copied. The other strand is the coding strand.
RNA polymerase adds ribonucleotides to the 3' end of the growing RNA strand in the 5' to 3' direction.
Uracil is used instead of thymine in RNA.

Steps of RNA Synthesis

Initiation: An initiation complex is formed using initiation protein factors and RNA polymerase, necessary to start the process.
Elongation: RNA polymerase moves along the template DNA, synthesizing RNA in the 5' to 3' direction. Elongation protein factors are needed for eukaryotes.
Termination: This step signifies the end of RNA synthesis.

Processing of Eukaryotic mRNA precursor

Capping: A 5' methyl guanosine cap is added to the mRNA to protect it and aid in ribosome binding.
Polyadenylation: A poly(A) tail is added to the 3' end of mRNA. This tail aids in mRNA stability and transport to the cytoplasm.

Genetic Code

mRNA contains four nucleotides (A, G, C, U).
Codons (three nucleotides) determine specific amino acids.
61 codons code for 20 amino acids.
3 codons are stop codons (UAA, UAG, UGA), signaling the end of translation.

Protein Biosynthesis

It's the flow of genetic information from DNA to protein.
Transcription produces mRNA, carrying genetic information from DNA to ribosomes.
Translation involves converting mRNA codons into an amino acid sequence.
Ribosomes act as the protein synthesis machinery, reading mRNA and assembling amino acids into a polypeptide chain.

Protein Synthesis Steps

Initial ribosomal dissociation into 40S and 60S subunits.
Formation of a pre-initiation complex including GTP, Met-tRNA, and the 40S subunit.
Formation of the 48S initiation complex.
Formation of the 80S initiation complex with the addition of the 60S subunit.
Elongation: involves multiple steps: -Binding of aminoacyl-tRNA to the A site. -Peptide bond formation between amino acids. -translocation moves peptidyl-tRNA to the P site.
Termination: release of the polypeptide chain when a stop codon is encountered. Release factors mediate hydrolysis of the peptide bond, releasing the protein.

Protein Processing

Proteins are modified after synthesis (proteolysis, glycosylation).
Proper folding is often important for protein function.
Molecular chaperones assist in protein folding.

Inhibitors of Protein Biosynthesis

Some antibiotics block prokaryotic protein synthesis, including streptomycin, tetracyclines, chloramphenicol, and erythromycin. Different antibiotics block different synthesis steps.

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Description

Test your knowledge on gene expression, including the processes of transcription and RNA synthesis. This quiz covers the key steps and components involved in transforming DNA into functional proteins. Understand the essential roles of RNA polymerase and the differences in strands during transcription.