Molecular Biology I - Lecture 6: Gene Expression
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Questions and Answers

What does the central dogma of molecular biology describe?

  • The synthesis of amino acids from nucleotides
  • The structure and function of genes in genomes
  • The conversion of genetic information from DNA to RNA to protein (correct)
  • The process of RNA replication

Which statement correctly describes the relationship between genes and genomes?

  • Two genes together make up a genome.
  • A gene is a complete set of nuclear DNA in a cell.
  • A genome includes all coding and non-coding DNA, whereas a gene is a segment of DNA. (correct)
  • Genomes are exclusively composed of coding DNA.

What is a defining characteristic of a gene compared to a genome?

  • A gene can be several million base pairs long.
  • A gene serves as a structural unit of heredity. (correct)
  • A genome cannot contain duplicate alleles.
  • A gene is defined only by its non-coding regions.

In the context of genetics, what does the term 'alleles' refer to?

<p>Variations of genes which can contribute to evolution (D)</p> Signup and view all the answers

What distinguishes the study of genes from the study of genomes?

<p>Gene studies focus on individual traits, while genome studies examine aggregate traits. (D)</p> Signup and view all the answers

Which statement accurately reflects the relationship between nucleotides in a gene and amino acids in the encoded protein?

<p>Colinearity holds true for bacterial genes but not necessarily for eukaryotic genes. (B)</p> Signup and view all the answers

What are exons primarily characterized by?

<p>They contain sequences that are highly conserved across species. (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of introns?

<p>Introns are present in both prokaryotes and eukaryotes. (C)</p> Signup and view all the answers

What happens to introns during the process of gene expression in eukaryotic cells?

<p>They are removed by RNA splicing, allowing exons to join. (A)</p> Signup and view all the answers

Which statement about eukaryotic genes is true regarding introns and exons?

<p>Eukaryotic genes typically contain more noncoding nucleotides than coding nucleotides. (D)</p> Signup and view all the answers

Which RNA polymerase is responsible for transcribing the 5.8S, 18S, and 28S rRNA genes?

<p>RNA polymerase I (C)</p> Signup and view all the answers

What is the role of the TATA box in eukaryotic transcription?

<p>It serves as a binding site for transcription factors. (B)</p> Signup and view all the answers

Which basal transcription factor is the first to bind to the TATA box during transcription initiation?

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

When eukaryotic protein-coding genes lack a TATA box, what alternative element may be present?

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

What is the primary function of RNA polymerase II within the nucleus?

<p>Transcribes pre-mRNA from protein-coding genes (B)</p> Signup and view all the answers

What is the approximate position of the TATA box relative to the transcription start site?

<p>It lies between positions -25 to -35. (D)</p> Signup and view all the answers

In eukaryotic transcription, what sequence is primarily recognized by RNA polymerase II at the promoter site?

<p>5’-TATAAA-3’ (B)</p> Signup and view all the answers

Which rRNA genes are transcribed by RNA polymerase I?

<p>18S rRNA genes (D)</p> Signup and view all the answers

What type of RNA is synthesized by RNA polymerase II?

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

What is the significance of the 'S' values assigned to rRNAs?

<p>They relate to the sedimentation rate in an ultracentrifuge. (C)</p> Signup and view all the answers

Which of the following best describes the structure of eukaryotic RNA polymerases?

<p>They show many structural similarities to bacterial RNA polymerase. (D)</p> Signup and view all the answers

What role do transcription factors play in eukaryotic transcription?

<p>They initiate the transcription process on DNA. (A)</p> Signup and view all the answers

How does eukaryotic transcription differ from prokaryotic transcription?

<p>Eukaryotic transcription involves multiple polymerases. (B)</p> Signup and view all the answers

Which of the following is true concerning the primary transcript produced during transcription?

<p>It results in a complementary, antiparallel mRNA strand. (D)</p> Signup and view all the answers

Which type of RNA is specifically associated with RNA polymerase III?

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

Flashcards

Central Dogma

The central dogma describes the flow of genetic information from DNA to RNA to protein. It's the process of converting DNA's information into a functional product.

Genome

A genome is the entire set of genetic instructions for an organism, including all coding and non-coding DNA. It encompasses all genes.

Gene

A gene is a segment of DNA that provides instructions for making a specific RNA or protein. It's the basic unit of heredity.

Genetics

The study of genes, their function, and their inheritance. Explores how genes are passed down from parents to offspring.

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Genomics

The study of complete sets of genes (genomes), including their structure, function, and evolution. Provides a comprehensive understanding of an organism's genetic makeup.

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Colinearity

The concept that the number of nucleotides in a gene directly corresponds to the number of amino acids in the protein it codes for.

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Introns

Non-coding DNA sequences found within genes of eukaryotes, removed during RNA splicing.

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Exons

Coding DNA sequences found within genes of eukaryotes, which are joined together after splicing to form mature mRNA.

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RNA splicing

The process of removing introns and joining exons in eukaryotic RNA transcripts.

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Non-coding vs. coding DNA

Eukaryotic genes often have more non-coding DNA (introns) than coding DNA (exons).

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What does RNA polymerase I transcribe?

RNA polymerase I is responsible for transcribing rRNA genes, which are essential for ribosome formation.

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What does RNA polymerase II transcribe?

RNA polymerase II transcribes mRNA genes, which carry genetic information from DNA to ribosomes for protein synthesis.

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What does RNA polymerase III transcribe?

RNA polymerase III transcribes tRNA genes, which are involved in protein synthesis by bringing amino acids to the ribosome.

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How many RNA polymerases are in eukaryotic cells?

Eukaryotic cells have three major RNA polymerases, each responsible for transcribing different types of RNA.

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Define Transcription

The process by which the information encoded in DNA is copied into a new molecule of RNA.

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What is the first step in gene expression?

The first step in gene expression, where a segment of DNA is copied into mRNA by RNA polymerase.

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What is a primary transcript?

The new strand of RNA produced during transcription, complementary and antiparallel to the DNA template.

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How does eukaryotic transcription differ from bacterial transcription?

Nucleosomes and chromatin structure are present in eukaryotic transcription, unlike in bacterial transcription.

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RNA polymerase I

RNA polymerase I transcribes rRNA genes (5.8S, 18S, and 28S) found in the nucleolus.

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RNA polymerase II

RNA polymerase II transcribes protein-coding genes, resulting in pre-mRNA. It's found in the nucleoplasm.

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RNA polymerase III

RNA polymerase III transcribes tRNA and 5S rRNA genes, located in the nucleoplasm.

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Promoter site

A specific DNA sequence located upstream of a gene, recognized by RNA polymerase to initiate transcription.

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TATA box

A highly conserved sequence within a promoter site for RNA polymerase II, located about 25-35 base pairs upstream of the start site.

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Basal transcription factors

A complex of proteins that assists RNA polymerase II in initiation of transcription. They bind to the promoter and help the polymerase attach.

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TBP (TATA box binding protein)

A subunit of the TFIID protein complex, specifically binding to the TATA box. It plays a crucial role in initiation.

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Study Notes

Molecular Biology I - Lecture 6: Gene Expression in Eukaryotes

  • The central dogma of molecular biology illustrates the flow of genetic information from DNA to RNA to protein.
  • DNA information is converted into a functional product.
  • Transcription is the process where DNA is transcribed into RNA.
  • In eukaryotes, the RNA transcript (pre-mRNA) is processed (spliced and modified) to become mRNA, which exits the nucleus and enters the cytoplasm.
  • Amino acids are activated, attached to tRNA molecules, which then bring them to the ribosome.
  • During translation, tRNAs add amino acids to a growing polypeptide chain as the mRNA is moved through the ribosome.
  • A gene is a segment of DNA that provides the instructions for making gene products (like RNA or proteins).
  • The genome includes all the DNA in an organism's nucleus (coding and non-coding DNA) and also the DNA in organelles like mitochondria.
  • A gene is composed of a few hundred base pairs, while a genome has millions of base pairs.
  • Genes have coding regions (exons) and noncoding regions (introns).
  • Introns are removed during RNA processing.
  • Introns are common in eukaryotic genes but are rare in bacterial genes.
  • Eukaryotes have three RNA polymerases, each responsible for transcribing different types of RNA. RNA polymerase I transcribes rRNA genes, RNA polymerase II transcribes mRNA genes, and RNA polymerase III transcribes tRNA and 5S rRNA genes.
  • Eukaryotic RNA polymerases require transcription factors to initiate transcription.
  • Transcription in eukaryotes occurs within the nucleus.
  • The basic mechanism of RNA synthesis in eukaryotes is divided into initiation, elongation, and termination phases.
  • The initiation phase involves RNA polymerase recognizing the promoter site, and RNA polymerase II requires transcription factors such as TFIID, TFIIB, TFIIA, TFIIE, TFIIF and TFIIH to recognize and bind to the promoter region.
  • During the elongation phase, the RNA polymerase moves along the DNA template, synthesizing RNA in the 5' to 3' direction.
  • The termination phase is when the RNA chain stops, and the primary transcript is released.

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Molecular Biology I BIO316 Lecture 6 PDF

Description

This quiz covers key concepts from Lecture 6 of Molecular Biology I, focusing on gene expression in eukaryotes. Topics include the central dogma, transcription, RNA processing, and translation. Understand the flow of genetic information and the roles of mRNA and tRNA in protein synthesis.

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