Molecular Biology Quiz: Transcription & Translation

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Questions and Answers

What is the primary function of tRNA during translation?

To bind to ribosomal RNA

To synthesize amino acids directly

To provide energy for protein synthesis

To transport amino acids to ribosomes (correct)

Which part of the ribosome is responsible for reading the mRNA during protein synthesis?

Small ribosomal subunit (correct)

Amino acid attachment site

tRNA binding site

Large ribosomal subunit

In the context of codon-anticodon interaction, what does the anticodon of tRNA do?

Pairs complementary to a codon on mRNA (correct)

Codes for the starting amino acid

Transports mRNA to the ribosome

Initiates the translation process

What process occurs when mRNA is converted into a protein?

Translation Signup and view all the answers

What role does aminoacyl-tRNA synthetase play in protein synthesis?

It attaches amino acids to the tRNA Signup and view all the answers

What is the correct sequence of processes involved in protein synthesis starting from DNA?

DNA → mRNA → Ribosome → Protein Signup and view all the answers

What is the role of tRNA in protein synthesis?

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

During mRNA processing, which of the following changes occurs?

Introns are removed and exons are joined together. Signup and view all the answers

What defines a codon in mRNA?

A sequence of three nucleotides. Signup and view all the answers

Which of the following best describes the function of ribosomes during translation?

They facilitate the assembly of amino acids into polypeptides. Signup and view all the answers

What occurs during the initiation phase of translation?

The ribosome assembles around the start codon on the mRNA. Signup and view all the answers

What happens at the termination stage of translation?

A stop codon on the mRNA is reached. Signup and view all the answers

Which nitrogenous base is unique to RNA and not found in DNA?

Uracil (U) Signup and view all the answers

What is the role of the 5' cap and 3' poly-A tail in mRNA processing?

Enhance the stability and export of mRNA from the nucleus Signup and view all the answers

During mRNA splicing, which components are removed from the pre-mRNA?

Introns Signup and view all the answers

What is the function of spliceosomes during RNA processing?

To join exons together after intron removal Signup and view all the answers

Which sequence signals the termination of transcription in eukaryotes?

AAUAAA Signup and view all the answers

What is the primary function of tRNA in protein synthesis?

To transport amino acids to the ribosome Signup and view all the answers

Which process involves the decoding of mRNA into a polypeptide chain?

Translation Signup and view all the answers

In the ribosome, which site is primarily responsible for holding the tRNA carrying the growing polypeptide chain?

P site Signup and view all the answers

What role do inducers play in the transcription regulatory process?

They remove repressors from their binding sites Signup and view all the answers

Study Notes

Transcription and Translation

DNA carries instructions to make proteins.
Protein synthesis involves transcription and translation.
Transcription: DNA's message is converted into RNA.
Translation: RNA message is used to assemble amino acids into a protein.

Central Dogma of Molecular Biology

DNA → mRNA → Protein
DNA replication occurs in the nucleus.
Transcription occurs in the nucleus.
mRNA travels to the ribosome in the cytoplasm for translation.

DNA vs. RNA

DNA: only in the nucleus, double-stranded, ATCG
RNA: in the nucleus and cytoplasm, single-stranded, AUCG
RNA has ribose sugar, DNA has deoxyribose sugar
RNA has uracil, DNA has thymine.

RNA Types

mRNA (messenger RNA): long strands complementary to DNA, carries genetic information.
rRNA (ribosomal RNA): associates with proteins to form ribosomes.
tRNA (transfer RNA): smaller segments that transport amino acids to the ribosome.

Codons and Amino Acids

3 nucleotides code for one amino acid.
Codons are found in mRNA.
Codon chart (picture included) shows correspondences between 3-letter codons and amino acids

Transcription

DNA→mRNA occurs in the nucleus.
Copies DNA's message into mRNA.
Pre-mRNA undergoes processing (5' cap, poly-A tail, removal of introns).
Processed mRNA leaves the nucleus to the cytoplasm.

Transcription process (Eukaryotes)

Initiation: RNA polymerase binds to promoter region (e.g, TATA box).
Elongation: RNA polymerase adds nucleotides to mRNA, using the DNA template strand.
Termination: RNA polymerase detaches when terminator sequence is reached.

Transcription regulation

Operon: a group of genes that are regulated together.
Promoter: DNA site that promotes RNA polymerase binding.
Repressor: molecule that binds to DNA to block transcription
Inducer: molecule that removes the repressor.

RNA Processing

Pre-mRNA → mRNA involves 5' capping, polyadenylation (3' poly-A tail).
Removal of introns by spliceosomes.
Results in mature mRNA leaving the nucleus.

Alternative RNA splicing

Introns: non-coding sections in pre-mRNA.
Exons: coding sections in pre-mRNA.
Splicing: removing introns, joining exons to form mRNA.

Translation

mRNA → protein in the cytoplasm.
Ribosomes assemble amino acids into proteins.

tRNA

tRNA: translator of mRNA's message; 80 nucleotides long; hairpin shape and anticodon; amino acid attachment site.
Anticodon (on tRNA) binds complementary to codon (on mRNA).
Each tRNA is specific to one amino acid.

Ribosomes

Ribosomes are made of rRNA and proteins.
They are decoding units (in the cytoplasm).
Three binding sites (A, P, E sites) align and help bind tRNAs to an mRNA molecule.
Ribosomes catalyze peptide bond formation.

Making a Protein

Initiation: small subunit binds to mRNA(start codon AUG).
Elongation: codon recognition, peptide bond formation, translocation.
Termination: Stop codon is reached, polypeptide is released.

Proteins

Fold spontaneously into primary, secondary, tertiary, and quaternary structures.
Chaperone proteins assist in folding.
Signal peptides direct proteins to their destination.

Targeting polypeptides

Signal peptides direct proteins through the endomembrane system.
SRP recognizes and binds to the signal peptide.
Protein synthesis resumes in the ER.
Signal peptide removed by enzymes.

Prokaryotes vs. Eukaryotes

Prokaryotes: no nucleus, simultaneous transcription and translation
Eukaryotes: nucleus separates transcription and translation, mRNA processing.

Mutations

Point mutations: one base altered; Base pair substitution
- Silent mutations: no effect on amino acid sequence
- Missense mutations: changes amino acid.
- Nonsense mutations: creates a stop codon.
Insertions/Deletions: Adds or removes bases, causes frameshift.
Frameshift mutations: alters the reading frame of mRNA.

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Description

Test your knowledge on the fundamental processes of molecular biology, including transcription and translation. This quiz covers the central dogma, the differences between DNA and RNA, and various types of RNA involved in protein synthesis. Challenge yourself to understand how genetic information is converted into functional proteins.