Gene Expression & Protein Synthesis Overview
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Questions and Answers

What is the primary role of messenger RNA (mRNA)?

  • To transfer amino acids
  • To serve as a template for making proteins (correct)
  • To provide structural support for ribosomes
  • To initiate transcription

Transcription occurs in the cytoplasm of eukaryotes.

False (B)

What are the two main elements that position RNA polymerase during transcription in prokaryotes?

The -10 element and the -35 element.

The process of creating a single-stranded RNA molecule from double-stranded DNA is called __________.

<p>transcription</p> Signup and view all the answers

Match the types of RNA with their main functions:

<p>mRNA = Template for protein synthesis tRNA = Brings amino acids to ribosomes rRNA = Structural component of ribosomes</p> Signup and view all the answers

Which component is most abundant in total RNA?

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

RNA polymerase requires transcription factors to initiate transcription in prokaryotes.

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

Where does transcription generally begin in a gene?

<p>At the promoter region.</p> Signup and view all the answers

The __________ region is typically located about 25 bases upstream from the startpoint for RNA polymerase II.

<p>TATA box</p> Signup and view all the answers

What percentage of total RNA does transfer RNA (tRNA) make up?

<p>15% (D)</p> Signup and view all the answers

What is the start point of transcription designated as?

<p>+1</p> Signup and view all the answers

In which direction is the new RNA strand synthesized during the elongation step?

<p>5’ to 3’ (A)</p> Signup and view all the answers

During the termination step, RNA polymerase disassembles from the DNA after reaching the termination site.

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

What is the completed RNA also known as after transcription?

<p>primary RNA transcript or pre-RNA</p> Signup and view all the answers

RNA polymerase reads the template strand in the __ direction during the elongation step.

<p>3’ to 5’</p> Signup and view all the answers

Match the stages of transcription with their descriptions:

<p>Elongation = Synthesis of RNA strand and untwisting of DNA Termination = Disassembly of RNA polymerase from DNA Proofreading = Replacement of incorrectly incorporated bases Processing = Addition of 5' cap and poly-A tail</p> Signup and view all the answers

Which of the following is not involved in RNA processing?

<p>Synthesis of RNA from DNA (D)</p> Signup and view all the answers

The RNA polymerase does not have any proofreading mechanism during transcription.

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

Why does RNA polymerase move along the DNA during transcription?

<p>To synthesize a new RNA strand.</p> Signup and view all the answers

The process of adding a poly-A tail to the __ end of the RNA is part of RNA processing.

<p>3’</p> Signup and view all the answers

What happens to the primary RNA transcript after transcription in eukaryotic cells?

<p>It undergoes further processing (A)</p> Signup and view all the answers

What is the main function of the cap and poly-A tail added to mRNA?

<p>To facilitate the export of RNA and protect it from degradation (A)</p> Signup and view all the answers

Introns are sequences that code for proteins.

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

What is the role of the spliceosome in RNA processing?

<p>The spliceosome removes introns and joins exons together.</p> Signup and view all the answers

A ______ is the sequence of three nucleotides on mRNA that codes for a specific amino acid.

<p>codon</p> Signup and view all the answers

Match the following components with their functions in translation:

<p>mRNA = Carries genetic information from DNA tRNA = Transfers amino acids to the ribosome Ribosome = Site of protein synthesis Release factor = Triggers termination of translation</p> Signup and view all the answers

Which codon is recognized as the start codon in mRNA?

<p>5'-AUG-3' (A)</p> Signup and view all the answers

Translation occurs in the nucleus of eukaryotic cells.

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

What is the significance of the wobble base in codons?

<p>The wobble base allows for variability in the third position of codons without changing the amino acid coded.</p> Signup and view all the answers

In eukaryotes, transcription and translation are ______ from each other.

<p>isolated</p> Signup and view all the answers

What happens during the termination phase of translation?

<p>The release factor binds to the stop codon and frees the polypeptide chain. (D)</p> Signup and view all the answers

Flashcards

Central Dogma of Biology

The process by which genetic information flows from DNA to RNA to proteins.

Transcription

The process of copying DNA into RNA.

RNA Polymerase

The enzyme that reads DNA and synthesizes RNA.

Promoter

A short DNA sequence that acts as a binding site for RNA polymerase, marking the start of a gene.

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-10 Sequence

A DNA sequence located 10 nucleotides upstream from the startpoint, important for transcription initiation.

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-35 Sequence

A DNA sequence located 35 nucleotides upstream from the startpoint, important for transcription initiation.

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Messenger RNA (mRNA)

The type of RNA that carries genetic information from DNA to ribosomes.

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Transfer RNA (tRNA)

The type of RNA that brings amino acids to ribosomes for protein synthesis.

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Ribosomal RNA (rRNA)

The type of RNA that makes up structural components of ribosomes.

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Transcription Factor

A protein that helps RNA polymerase recognize and bind to the promoter.

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Transcription (Elongation)

The process that builds a new RNA molecule from a DNA template. This occurs in the 5' to 3' direction, meaning that new nucleotides are added to the 3' end of the growing RNA molecule, starting from the 5' end. This process is essential for gene expression.

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Template Strand (Transcription)

The DNA strand being copied during transcription. It is read in the 3' to 5' direction by the RNA polymerase.

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Promoter Region

The place on the DNA molecule where transcription begins. It signals RNA polymerase to bind and start making RNA.

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Termination Sequence

The special sequence of DNA that tells RNA polymerase where to stop transcription. It signals the end of the RNA molecule.

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Primary RNA Transcript (pre-RNA)

The newly synthesized RNA molecule that has not yet been processed.

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RNA Processing

The process of modifying the primary RNA transcript to make it functional. It involves capping, tailing, and splicing.

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5' Cap (RNA Processing)

A special chemical modification added to the 5' end of the primary RNA transcript. This modification is important for protecting the RNA molecule and helping it bind to ribosomes.

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Poly-A Tail (RNA Processing)

A sequence of adenine nucleotides (A) added to the 3' end of the primary RNA transcript. This modification helps regulate the RNA molecule's stability and lifespan.

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Intron Splicing

A process that removes non-coding sequences (introns) from pre-mRNA, leaving only coding sequences (exons).

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Spliceosome

A large complex made of snRNAs and proteins that carries out intron splicing in eukaryotes.

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5' Cap

A 7-methyl guanosine triphosphate molecule added to the 5' end of mRNA during RNA processing.

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Poly-A tail

A string of 100-250 adenine nucleotides added to the 3' end of mRNA during RNA processing.

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Translation

The process of converting genetic information from mRNA into a protein.

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Ribosome

The cellular machinery responsible for protein synthesis, composed of two subunits: large and small.

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Initiation

The stage of translation where the ribosome binds to mRNA and the first tRNA carrying methionine binds to the start codon.

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Elongation

The stage of translation where the polypeptide chain grows by adding amino acids one by one.

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Termination

The stage of translation where the polypeptide chain is released from the ribosome.

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Study Notes

Gene Expression & Protein Synthesis Overview

  • Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product, typically a protein.
  • The central dogma of biology describes the flow of genetic information from DNA to RNA to proteins.

The Central Dogma

  • Genetic information flows from DNA to RNA to proteins.
  • Replication is the process of creating a copy of DNA
  • Transcription is the process of making RNA from a DNA template.
    • Occurs in the nucleus of eukaryotes
    • Occurs in the cytoplasm of prokaryotes
  • Translation is the process of using the information in RNA to create a protein. Occurs in the cytoplasm.

Types of RNA

  • Messenger RNA (mRNA): Used as a template to make proteins; 3-5% of total RNA
  • Transfer RNA (tRNA): Brings amino acids to mRNA and ribosomes; ~15% of total RNA
  • Ribosomal RNA (rRNA): Makes up ribosomes; ~80% of total RNA

Transcription Details

  • A portion of double-stranded DNA is transcribed into a single-stranded RNA molecule.
  • Initiation: RNA polymerase binds to the promoter region on the gene.
  • Elongation: RNA polymerase moves along the DNA template strand, synthesizing the RNA molecule.
  • Termination: RNA polymerase reaches a termination sequence and stops, releasing the newly made RNA molecule.

Eukaryotic Promoter

  • Typically found near the beginning of a gene.
  • Contains a TATA box, a short DNA sequence (~25 bases upstream) that is critical for RNA polymerase binding.

Prokaryotic Promoter

  • Contains a -10 and -35 sequence (located 10 and 35 nucleotides upstream to the startpoint) that help RNA polymerase bind to the DNA.
  • The two elements position the RNA polymerase and determine the direction it operates.

Transcription Elongation

  • RNA polymerase synthesizes RNA in a 5' to 3' direction.
  • The template strand is read in the 3' to 5' direction.
  • RNA polymerase untwists a portion of DNA double helix.
  • The polymerase has a proofreading mechanism.

Termination Step

  • End point of transcription where RNA polymerase disassembles from DNA.
  • RNA typically called primary RNA transcript before processing

Post-Transcription Processing (Eukaryotes)

  • Addition of a cap to the 5' end of RNA
  • Addition of a poly-A tail to the 3' end of RNA
  • Removal of introns (non-coding regions) and joining of exons (coding regions).

Introns and Exons

  • Introns: Non-coding sequences removed during RNA processing.
  • Exons: Coding sequences that make up the final mRNA.

Intron Splicing

  • Introns are removed by spliceosomes while the RNA is still in the nucleus.
  • Spliceosome is a complex of small nuclear RNAs and proteins.

Translation

  • The process of "decoding" mRNA and assembling a protein.
  • Major players: mRNA, tRNA, ribosomes, amino acids.
  • Four phases: activation, initiation, elongation, termination

Messenger RNA (mRNA)

  • Single-stranded RNA molecule complementary to a DNA template.
  • Carries genetic instructions from DNA to cytoplasm.
  • mRNA is read in codons (3 nucleotides each) that specify amino acids.

Genetic Code

  • Almost universal; used by both prokaryotes and eukaryotes.

  • 64 codons, but code for 20 amino acids.

  • Degenerate means that more than one codon codes for most amino acids.

  • Wobble base allows for some flexibility in mRNA base pairings.

  • AUG (methionine) is the start codon.

  • UAA, UAG, and UGA are stop codons.

Ribosomes

  • Protein factories of cells.
  • Made of two subunits: large and small.
  • Three sites: A site (aminoacyl-tRNA), P site (peptidyl-tRNA), and E site (exit site).

Translation Initiation

  • mRNA, tRNA carrying methionine (initiator tRNA), and small ribosomal subunit come together.
  • The complex forms at the 5' end of mRNA (ribosome binding site)
  • The Large subunit of the ribosome finishes the initiation complex using GTP.

Translation Elongation

  • Incoming tRNA with amino acid binds to A site.
  • Polypeptide chain is moved from P site to new amino acid at the A site.
  • Empty tRNA moves to the E site then exits.

Translation Termination

  • Stop codon recognized by a release factor.
  • Polypeptide chain is cleaved.
  • Ribosomal subunits and mRNA dissociate.

Coupled Transcription and Translation (Prokaryotes)

  • Transcription and translation occur simultaneously in bacteria.
  • Ribosomes attach to mRNA as it's being synthesized.

Monocistronic vs. Polycistronic mRNA

  • Monocistronic: One type of protein from a single mRNA molecule (eukaryotes)
  • Polycistronic: Multiple protein types from a single mRNA molecule (prokaryotes)

Transfer RNA (tRNA)

  • Has an anticodon that pairs with a codon on mRNA.
  • Carries specific amino acids to the ribosome.

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BISC 101 - Gene Expression & Protein Synthesis PDF

Description

Explore the fundamental processes of gene expression and protein synthesis in this informative quiz. Understand the central dogma of biology, transcription, and translation, along with the different types of RNA involved in these processes. Test your knowledge and deepen your understanding of molecular biology.

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