Biology 1001, Section 9: From Gene to Protein
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Biology 1001, Section 9: From Gene to Protein

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Questions and Answers

What is the first step in the flow of information from DNA to protein?

  • DNA is replicated before protein synthesis
  • Proteins are synthesized from mRNA
  • mRNA is translated into the amino acid sequence
  • RNA transcribes the DNA template strand (correct)

    • Which nucleotide replaces thymine in RNA during transcription?

  • Adenine
  • Guanine
  • Cytosine
  • Uracil (correct)

    • What does each codon on an mRNA molecule specify?

  • A specific type of nucleotide
  • A gene sequence
  • A particular amino acid (correct)
  • A type of RNA molecule

    • Which statement correctly defines a gene?

    <p>A region of DNA that produces a functional product</p> Signup and view all the answers

    In regards to the DNA structure, which statement is true?

    <p>Both strands of DNA can contain genes</p> Signup and view all the answers

    What is the primary end product of transcription in cases where it does not proceed to translation?

    <p>rRNA or tRNA</p> Signup and view all the answers

    How many nucleotides are present in RNA to form the genetic code?

    <p>4</p> Signup and view all the answers

    Which statement accurately describes the difference in transcription and translation between bacteria and eukarya?

    <p>Eukaryotic mRNA is processed after transcription.</p> Signup and view all the answers

    What is the concept that links nucleic acids to proteins?

    <p>The genetic code</p> Signup and view all the answers

    Which combination of nucleotide words can translate to 16 different amino acids?

    <p>Using 2-letter words</p> Signup and view all the answers

    What is an example of an RNA type that is used without being translated into protein?

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

    What arrangement of nucleotide letters allows for the possibility of creating 20 different amino acids?

    <p>Nucleotide words of 3 letters</p> Signup and view all the answers

    What is the term used for the DNA strand that is transcribed to produce RNA?

    <p>Template strand</p> Signup and view all the answers

    What occurs in bacteria that differentiates their transcription process from eukaryotes?

    <p>Transcription occurs in the cytoplasm.</p> Signup and view all the answers

    In what direction is RNA synthesized during transcription?

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

    Which enzyme is primarily responsible for the synthesis of RNA during transcription?

    <p>RNA polymerase</p> Signup and view all the answers

    During which stage of transcription does RNA polymerase unwound the DNA to initiate transcription?

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

    What occurs during the elongation phase of transcription?

    <p>RNA polymerase synthesizes RNA while unwinding DNA</p> Signup and view all the answers

    What is the first step in the process of gene expression according to current knowledge?

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

    What role does messenger RNA (mRNA) play in gene expression?

    <p>It carries instructions for protein synthesis</p> Signup and view all the answers

    Which of the following statements about proteins is true?

    <p>Proteins determine phenotypic traits of organisms.</p> Signup and view all the answers

    According to the Central Dogma, what is the correct sequence of information flow?

    <p>DNA → RNA → Protein</p> Signup and view all the answers

    What happens during the process of transcription?

    <p>The instructions from DNA are copied onto RNA.</p> Signup and view all the answers

    In eukaryotic cells, which modification to RNA occurs after transcription?

    <p>Addition of cap and tail</p> Signup and view all the answers

    What is the primary purpose of gene expression?

    <p>Production of proteins</p> Signup and view all the answers

    Which component is not directly involved in the synthesis of proteins?

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

    What distinguishes prokaryotic mRNA from eukaryotic mRNA immediately after transcription?

    <p>Prokaryotic mRNA is ready for translation right away.</p> Signup and view all the answers

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

    <p>A poly-A tail of adenine nucleotides.</p> Signup and view all the answers

    What role does the 5' cap play in mRNA processing?

    <p>It helps export mRNA from the nucleus.</p> Signup and view all the answers

    How does transcription and translation occur in prokaryotes?

    <p>They occur simultaneously.</p> Signup and view all the answers

    What are the non-coding segments of mRNA called that lie between the start and stop codons?

    <p>Introns.</p> Signup and view all the answers

    Which statement accurately describes how eukaryotic mRNA is processed?

    <p>It involves adding a 5’ cap and a poly-A tail.</p> Signup and view all the answers

    What is a consequence of prokaryotic mRNA not requiring additional processing?

    <p>It allows for rapid protein production from single genes.</p> Signup and view all the answers

    Which function do the 5' cap and poly-A tail share?

    <p>They both provide protection from hydrolytic enzymes.</p> Signup and view all the answers

    What is the primary function of introns in the context of gene expression?

    <p>They allow alternative RNA splicing to occur.</p> Signup and view all the answers

    Which component is primarily responsible for the actual splicing of introns from the mRNA molecule?

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

    How many codons are needed to code for a protein that is 146 amino acids long?

    <p>438</p> Signup and view all the answers

    What role do small RNA molecules play in the process of splicing?

    <p>They identify and bind to introns for removal.</p> Signup and view all the answers

    What is a potential reason for the presence of introns in eukaryotic genes?

    <p>They may represent remnants of viral DNA integration.</p> Signup and view all the answers

    What is meant by 'alternative RNA splicing'?

    <p>It allows for different proteins to be produced from the same gene.</p> Signup and view all the answers

    In the context of gene complexity, what can be inferred from the comparison between humans and roundworms?

    <p>Alternative splicing contributes to increased complexity despite similar gene numbers.</p> Signup and view all the answers

    Where are introns primarily removed from during the gene expression process?

    <p>Before mRNA exits the nucleus</p> Signup and view all the answers

    Study Notes

    Biology 1001, Section 9: From Gene to Protein

    • Genes control an organism's phenotypic traits (appearance and physiology).
    • Genes contain instructions for making proteins, but these instructions are not used directly and copied onto RNA molecules.
    • Messenger RNA (mRNA) carries these instructions to protein-making machinery (ribosomes) in the cytoplasm.
    • Proteins are the link between DNA and characteristics. Different types of proteins perform diverse functions.
    • Transcription is the process of DNA-directed RNA synthesis. This process begins at the promoter region. RNA polymerase works along the template strand in a 3' to 5' direction and creates a complementary copy of RNA, substituting uracil for thymine.
    • Translation converts RNA to amino acid. It uses mRNA to manufacture a polypeptide as a protein. mRNA directs the synthesis of a polypeptide, specifying which amino acid will be sequentially added.
    • The genetic code is a series of three nucleotides called codons. This three-nucleotide code translates to 20 different amino acids.
    • Codons for all 20 amino acids have been identified and deciphered.
    • mRNA is translated without any additional processing in prokaryotes, but in eukaryotes, pre-mRNA is processed to produce mRNA inside the nucleus before export to the cytoplasm. Modifications include the addition of a 5' cap and a poly-A tail.
    • Introns are non-coding regions within eukaryotic genes; Exons are the sections of DNA sequence that code for proteins.
    • Introns are removed by a process called splicing, the introns are retained in the nucleus, and exons are connected to produce a continuous coding sequence.
    • Splicing happens Inside the nucleus and is done by spliceosomes within the mRNA.
    • Introns may have evolutionary reasons or may be "selfish" DNA.
    • The genetic code is universal, implying a common ancestry for all organisms.
    • Prokaryotes and eukaryotes have similar ribosomes, which are made of proteins and rRNA. Ribosomes are responsible for positioning mRNA and tRNA during protein synthesis.
    • Protein synthesis takes place within ribosomes, and three sites (A, P, and E).

    Summary of transcription and Translation

    • Transcription happens in the nucleus using the DNA template and produces mRNA
    • mRNA leaves the nucleus then goes to a ribosome
    • The ribosome reads the codons on the mRNA molecule
    • tRNAs deliver the correct amino acid according to the mRNA instructions
    • Amino acids are linked together by peptide bonds, producing a polypeptide chain
    • This chain folds to become a functional protein
    • Eukaryotic cells produce pre-mRNA which is processed and modified, then exported to the cytoplasm (creating mRNA)
    • Prokaryotic cells are simpler, as translation can start immediately.
    • The overall process of creating proteins from genes is called gene expression.

    Basic Mechanisms of Transcription and Translation

    • Bacteria lack a nuclear membrane; this leads to the transcription and translation processes being concurrent.
    • In eukaryotes, transcription occurs inside the nucleus, while translation takes place outside the nucleus in the cytoplasm. Pre-mRNA must be processed first.
    • mRNA has a 5' cap and 3' poly-A tail that protect mRNA and assist in export from the nucleus.
    • Introns must be removed from pre-mRNA by splicing.
    • The product, mature mRNA, moves to the cytoplasm and is used by ribosomes which translate it.

    Steps Of Translation Initiation

    • The small ribosomal subunit binds to mRNA. A specific tRNA with methionine (the initiator tRNA) connects to the start codon on the mRNA.
    • The large ribosomal subunit joins the complex to initiate translation.
    • The initiator tRNA sits in the P site on the growing peptide and initiates translation.

    Building a Polypeptide

    • Steps of elongation: Incoming tRNAs bring their amino acids to the A site, a peptide bond forms between amino acids, and the ribosome shifts.
    • Termination: a stop codon on the mRNA signals the termination of translation, the release factor protein dissociates the polypeptide from the last tRNA, and the ribosome subunits disassemble.

    Ribosome Structure and Function

    • Ribosomes contain rRNA and proteins.
    • Ribosomes have three binding sites (A, P, and E) for tRNAs and an exit tunnel to release polypeptide chains.
    • rRNA directs the positioning of mRNA and tRNA, catalyzes peptide bond formation.

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    Biology 1001 Unit 9: DNA to Protein PDF

    Description

    Explore the fascinating journey from genes to proteins in this quiz. Understand the processes of transcription and translation, and how proteins link DNA to phenotypic traits. Test your knowledge on the roles of mRNA and the genetic code in protein synthesis.

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