Gene Expression and Protein Structure
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Questions and Answers

What is the main purpose of mRNA processing?

  • To replicate DNA
  • To facilitate the breakdown of mRNA
  • To modify mRNA for translation (correct)
  • To remove exons from the RNA sequence

    • Which nitrogenous base is found in RNA but not in DNA?

  • Adenine (A)
  • Uracil (U) (correct)
  • Cytosine (C)
  • Thymine (T)

    • During transcription, what role does RNA polymerase play?

  • It transports mRNA to the ribosome
  • It unwinds the DNA segment (correct)
  • It synthesizes proteins directly
  • It bonds amino acids together

    • What happens to the RNA molecule after it is synthesized?

    <p>It is processed and modified</p> Signup and view all the answers

    How does the structure of DNA differ from that of RNA?

    <p>DNA is double-stranded, RNA is single-stranded</p> Signup and view all the answers

    What is the significance of the Guanine Cap and Poly A tail in mRNA?

    <p>They prevent degradation of mRNA</p> Signup and view all the answers

    Which of the following is true about introns?

    <p>They are removed during mRNA splicing</p> Signup and view all the answers

    Where does mRNA processing occur in eukaryotic cells?

    <p>In the nucleus</p> Signup and view all the answers

    What function does the 5' cap serve in the primary mRNA transcript?

    <p>It stabilizes the mRNA and aids in ribosome binding.</p> Signup and view all the answers

    Which regions of DNA are transcribed but not translated?

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

    Which of the following is true about mature mRNA?

    <p>It includes exons, a guanine cap, and a poly A tail.</p> Signup and view all the answers

    What is the role of codons in the process of translation?

    <p>They determine the sequence of amino acids in a protein.</p> Signup and view all the answers

    Which process is responsible for removing introns from the pre-mRNA?

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

    What is the significance of the universal nature of the DNA code?

    <p>It allows any organism to use the same 20 amino acids.</p> Signup and view all the answers

    Where does the process of translation take place within the cell?

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

    Which component is NOT included in the primary mRNA transcript?

    <p>Poly A tail</p> Signup and view all the answers

    What is the primary function of tRNA in the process of translation?

    <p>To bind and transport amino acids to the ribosome</p> Signup and view all the answers

    What feature of tRNA allows it to bind to the corresponding mRNA codon?

    <p>The anticodon region</p> Signup and view all the answers

    Which nucleotide sequence represents the anticodon for the mRNA codon UGG?

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

    Which of the following statements about the start codon is true?

    <p>It codes for methionine in eukaryotes.</p> Signup and view all the answers

    During translation, what happens to the tRNA molecule once it has delivered its amino acid?

    <p>It is recycled back to the cytoplasm.</p> Signup and view all the answers

    What is the initial step in the process of translation initiation?

    <p>The small ribosomal subunit assembles at the start codon.</p> Signup and view all the answers

    How does the ribosome move along the mRNA during translation?

    <p>One codon at a time</p> Signup and view all the answers

    What is the role of the ribosomal RNA (rRNA) in the translation process?

    <p>It binds with mRNA and stabilizes the ribosome structure.</p> Signup and view all the answers

    What symptom would likely arise from a deficiency in lactase?

    <p>Inability to digest lactose found in milk</p> Signup and view all the answers

    Which component of a nucleotide differs between DNA and RNA?

    <p>Sugar type</p> Signup and view all the answers

    What is the primary function of hemoglobin in red blood cells?

    <p>Transports oxygen</p> Signup and view all the answers

    What characterizes the structure of DNA?

    <p>Double-stranded and antiparallel</p> Signup and view all the answers

    What condition results from a deficiency in clotting proteins?

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

    Which of the following nitrogenous bases is present only in RNA?

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

    What is the role of acetaldehyde dehydrogenase in the body?

    <p>Breaking down acetaldehyde from alcohol</p> Signup and view all the answers

    How are nucleotides linked within a single strand of DNA?

    <p>Covalent bonds</p> Signup and view all the answers

    What is the primary cause of sickle-cell anemia?

    <p>A mutation in the gene for hemoglobin</p> Signup and view all the answers

    Which point mutation is most likely to result in a nonfunctional protein?

    <p>Both nucleotide deletion and insertion</p> Signup and view all the answers

    How do repair enzymes contribute to genetic stability?

    <p>They correct errors during DNA replication</p> Signup and view all the answers

    Which of the following statements about mutations is correct?

    <p>Most mutations do not significantly affect survival</p> Signup and view all the answers

    What accurately describes a nucleotide deletion?

    <p>It can cause a frameshift mutation.</p> Signup and view all the answers

    Which environmental factor is classified as a mutagen?

    <p>UV radiation</p> Signup and view all the answers

    Which type of mutation is least likely to change the amino acid sequence?

    <p>Nucleotide substitution</p> Signup and view all the answers

    What is a common outcome of a frameshift mutation?

    <p>The alteration of multiple amino acids</p> Signup and view all the answers

    What forms the sides of the DNA ladder structure?

    <p>Phosphate and sugar molecules</p> Signup and view all the answers

    What is the significance of complementary base pairing in DNA?

    <p>It ensures that T binds with A and C binds with G</p> Signup and view all the answers

    During DNA replication, which enzyme is responsible for adding new nucleotides?

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

    Which of the following describes the structure of the DNA double helix?

    <p>A coiled structure resembling a twisted ladder</p> Signup and view all the answers

    What are histones in relation to DNA?

    <p>Proteins that help package DNA into chromatin</p> Signup and view all the answers

    What is the result of DNA replication?

    <p>Two identical DNA molecules, each with one old and one new strand</p> Signup and view all the answers

    Why is DNA replication described as occurring in many places simultaneously?

    <p>To speed up the replication process</p> Signup and view all the answers

    What is the approximate number of chromosomes in a human body cell?

    <p>46</p> Signup and view all the answers

    Study Notes

    Gene Expression and Proteins

    • Proteins are formed from different arrangements of 20 amino acids, like words from letters.
    • Humans can make some amino acids but need others (essential amino acids) from food.
    • Proteins differ based on the number of amino acids (length), order of amino acids, and type of amino acids.
    • Amino acids are grouped by chemical properties, like hydrophobic (nonpolar), polar, and charged.
    • Hydrophobic amino acids tend to be nonpolar; they frequently interact with each other.
    • Polar amino acids have groups that attract water; they often participate in hydrogen bonding and other interactions.
    • Charged amino acids have charged groups that interact with other charged groups.
    • Cysteine amino acids are capable of forming disulfide bridges with other cysteine amino acids.

    Protein Structure

    • Primary structure: Linear sequence of amino acids, held together by peptide bonds.
    • Secondary structure: Local folds (alpha helices, beta sheets) formed by hydrogen bonds.
    • Tertiary structure: 3-D shape resulting from R-group interactions, including hydrophobic interactions, hydrogen bonds, ionic bonding, and disulfide bonds (ex. final or functional protein)
    • Quaternary structure: Multiple polypeptide chains combining to form a functional protein.

    Sickle Cell Anemia

    • A disease caused by a mutation in the hemoglobin protein. One change in an amino acid sequence causes a change in hemoglobin structure.
    • In hemoglobin, the order leads to red blood cells having a sickle shape, preventing efficient oxygen transport.

    Protein Denaturation

    • Loss of secondary, tertiary, or quaternary structure due to factors like high temperatures, extreme pH, and high salt concentrations.
    • These factors disrupt stabilizing interactions (e.g., hydrogen bonds, ionic bonds, and disulfide bridges).

    Proteins Determine Traits

    • All cells have genetic material in the form of DNA.
    • Genes code for proteins that determine traits.
    • Genes directly influence organism characteristics.

    Nucleic Acids

    • Two main types of nucleic acids: DNA and RNA.
    • Nucleotides are the building blocks of nucleic acids.
    • Each nucleotide has a sugar (ribose or deoxyribose), a nitrogenous base (A, T, C, G, or U), and a phosphate group.
    • DNA is double-stranded in a double helix shape, and RNA is single-stranded with a different sugar and bases
    • DNA and RNA have different sugars. DNA has deoxyribose, and RNA has ribose.
    • DNA has thymine, and RNA has uracil.
    • DNA is typically larger than RNA in a cell.
    • DNA strands run antiparallel, meaning they are oriented in opposite directions.

    DNA Replication

    • The process of copying DNA prior to cell division to ensure each new cell gets a complete copy of the genetic material.
    • DNA replication is semi-conservative, one strand from the parent DNA and a newly synthesized strand.

    Gene Expression Protein Building: Transcription and Translation

    • Transcription: DNA code copied into mRNA.
    • Translation: mRNA code used to assemble amino acids into a protein.
    • mRNA: Messenger RNA
    • tRNA: Transfer RNA
    • rRNA: Ribosomal RNA
    • Ribosomes are the site of protein synthesis.

    Mutations

    • Changes in DNA sequence.
    • Most, but not all mutations are harmful.
    • Mutations can lead to altered proteins that may have impaired function.
    • Some mutations can be beneficial or neutral.
    • Mutations can be caused by errors in DNA replication, exposure to environmental mutagens.
    • Deletions and additions can shift the reading frame, meaning the sequence of amino acids is altered from the point of the mutation forward. Substitution of a nucleotide can lead to different amino acids (e.g. sickle cell).

    Point Mutations

    • Changes in a single nucleotide.
    • Substitution: Replace one nucleotide with another.
    • Deletion: Removing a nucleotide.
    • Insertion: Adding a nucleotide.
    • Frameshift mutations (insertion or deletion) result in changes in the reading frame, affecting the entire amino acid sequence downstream from the mutation.

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    Honors Biology 2A: Gene Expression - McCarthy 24-25 PDF

    Description

    Explore the fascinating world of protein formation and structure in this quiz. Learn about the various amino acids, their properties, and how they combine to create functional proteins. Discover the significance of primary and secondary protein structures in biological systems.

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