Nucleotides and DNA Structure Quiz
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Questions and Answers

What are the two types of nucleic acid?

  • Proteins and Lipids
  • DNA and RNA (correct)
  • DNA and Amino Acids
  • RNA and Proteins

    • What are nucleotides made of?

    A sugar (deoxyribose or ribose), a phosphate group, and a nitrogen-containing base.

    Which of the following are purine bases?

  • Uracil and Cytosine
  • Thymine and Cytosine
  • Adenine and Guanine (correct)
  • Adenine and Uracil

    • Which of the following is not a pyrimidine base?

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

    The linkage of a base to a sugar via an N-glycosidic bond is called a nucleoside.

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

    The linkage of a nucleoside to a phosphate group is called a nucleotide.

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

    What does the prefix 'deoxy' stand for?

    <p>The absence of an oxygen atom</p> Signup and view all the answers

    Nucleic acids contain only nucleoside monophosphates.

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

    Only nucleoside triphosphates can act as high-energy phosphate compounds.

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

    Match the following RNA bases to their corresponding nucleoside and nucleotide.

    <p>Adenine (A) = Adenosine, Adenylate (AMP) Guanine (G) = Guanosine, Guanylate (GMP) Uracil (U) = Uridine, Uridylate (UMP) Cytosine (C) = Cytidine, Cytidylate (CMP)</p> Signup and view all the answers

    Match the following DNA bases to their corresponding deoxyribonucleoside and deoxyribonucleotide.

    <p>Adenine (A) = Deoxyadenosine, Deoxyadenylate (dAMP) Guanine (G) = Deoxyguanosine, Deoxyguanylate (dGMP) Thymine (T) = Thymidine, Thymidylate (TMP) Cytosine (C) = Deoxycytidine, Deoxycytidylate (dCMP)</p> Signup and view all the answers

    What type of bond links nucleotides together in a polynucleotide chain?

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

    The two strands of a DNA double helix run in the same direction.

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

    What type of bonding is responsible for holding the two strands of a DNA double helix together?

    <p>Hydrogen bonding</p> Signup and view all the answers

    The hydrophobic interactions between the stacked bases help to stabilize the DNA double helix.

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

    What are the two grooves that are present on the exterior of a DNA double helix called?

    <p>Major and minor grooves</p> Signup and view all the answers

    In humans, each cell contains 46 chromosomes with a total length of one meter.

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

    What is chromatin?

    <p>Chromatin is the complex of DNA and proteins that make up chromosomes. It's essentially the packaged form of DNA found in the nucleus of eukaryotic cells.</p> Signup and view all the answers

    What type of proteins are histones?

    <p>Basic proteins</p> Signup and view all the answers

    Histones are involved in regulating gene expression.

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

    What is a nucleosome?

    <p>A nucleosome is the basic unit of chromatin, consisting of a segment of DNA wrapped around a core of histone proteins, along with a linker DNA region.</p> Signup and view all the answers

    The linker DNA region connects adjacent nucleosomes.

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

    Which of the following describes how chromatin is further compacted beyond nucleosomes?

    <p>All of the above</p> Signup and view all the answers

    The centromere is a region on a chromosome that is rich in A-T base pairs.

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

    What role do kinetochores play in chromosome segregation?

    <p>Kinetochores are protein complexes that attach to the centromere of chromosomes, serving as the point of attachment for the spindle fibers during cell division. This connection ensures the proper segregation of chromosomes to daughter cells, guaranteeing the correct distribution of genetic material in each new cell.</p> Signup and view all the answers

    Study Notes

    Nucleotides, DNA Structure & Organization

    • Nucleic acids include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
    • Each nucleic acid is composed of nucleotides.
    • A nucleotide consists of:
      • A sugar (deoxyribose or ribose)
      • A phosphate group
      • A nitrogen-containing base
    • Purine bases (adenine [A], guanine [G]) have two rings.
    • Pyrimidine bases (thymine [T], cytosine [C], uracil [U]) have one ring.
    • Linking a base to a sugar creates a nucleoside.
    • Linking a nucleoside to a phosphate group forms a nucleotide.
    • Nucleotides can be further categorized as:
      • Nucleoside monophosphate
      • Nucleoside diphosphate
      • Nucleoside triphosphate
    • Nucleic acids contain nucleoside monophosphates.
    • High-energy phosphate compounds can be tri-, di-, or monophosphates of nucleosides.

    Importance of Nucleotides & Nucleosides & Nitrogenous Bases

    • Nucleotides participate in the synthesis of nucleic acids (DNA and RNA).
    • Nucleotides like ATP and GTP serve as high-energy phosphate compounds.
    • Nucleotides play roles as coenzymes (e.g., NAD, NADP, FAD, FMN, coenzyme A, deoxyadenosylcobalamine).
    • Nucleotides act as donors in various metabolic pathways (e.g., UDP-glucose, UDP-glucuronic acid, S-adenosylmethionine, CDP-choline, CDP-ethanolamine).
    • Nitrogenous bases act as secondary messengers for hormones (e.g., cAMP, cGMP).
    • Methylated nitrogenous bases are important in regulating gene expression.
    • Synthetic purine and pyrimidine analogs have medicinal applications (e.g., allopurinol for gout, 5-fluorouracil for cancer).

    DNA

    • DNA is the genetic material carrying the individual's genetic information.
    • In eukaryotes, DNA is primarily located in the chromosomes of the nucleus and in mitochondria.
    • In prokaryotes, DNA is found in the single chromosome and plasmids.
    • DNA has the functions of:
      • Storing genetic information
      • Transferring genetic information to daughter cells during replication
    • DNA must replicate precisely during cell division to ensure each daughter cell receives the same genetic material.
    • Nuclear DNA encodes functional proteins and functional RNA.
    • Mitochondrial DNA contains genes for proteins in the electron transport chain and ribosomal and transfer RNAs.

    DNA Structure

    • DNA consists of two chains (strands) that wind around each other in a double helix. (Watson-Crick model)
    • Each strand is formed of deoxyribonucleotides linked by 3'-5' phosphodiester bonds between sugars and phosphates.
    • Each deoxyribonucleotide is composed of:
      • A deoxyribose sugar
      • A phosphate group
      • A nitrogenous base (A, T, G, C)
    • The 5' end has a free phosphate group, and the 3' end has a free hydroxyl group.
    • DNA replication proceeds in a 5' to 3' direction.
    • The hydrophilic (polar) deoxyribose-phosphate backbone is on the outside of the DNA molecule.
    • Hydrophobic (nonpolar) bases are stacked inside, perpendicular to the helix axis.

    DNA Antiparallel Strands

    • The two DNA strands run antiparallel to each other.
    • One strand is oriented 5' to 3', and the other is 3' to 5'.
    • Hydrogen bonds between bases and hydrophobic interactions between stacked bases stabilize the double helix.

    Base Pairing Rules

    • Thymine pairs with adenine (2 hydrogen bonds).
    • Cytosine pairs with guanine (3 hydrogen bonds).
    • The base-pairing rules ensure that one strand is complementary to the other.
    • G-C base pairs are more stable than A-T base pairs due to the stronger hydrogen bonding.

    DNA Major and Minor Grooves

    • DNA has two grooves: major and minor grooves, on its exterior surface.
    • These grooves result from the unequal size of the grooves due to the asymmetry of deoxyribose rings and structural differences in the upper surface of a base pair.

    DNA Organization

    • In humans, each cell contains 46 chromosomes whose total length is approximately one meter.
    • Chromosomes must condense into chromatin to fit within the nucleus.
    • Chromatin comprises:
      • Nuclear DNA
      • Histone proteins
      • Smaller amounts of nonhistone proteins (e.g., enzymes involved in DNA replication and transcription).
      • Small amounts of RNA (e.g., snRNA).

    Histones

    • Histones are basic proteins with positive charges, enabling ionic bonds with negatively charged DNA.
    • Five types of histones exist: H1, H2A, H2B, H3, and H4.
    • Histones help condense DNA into compact chromosomes.
    • Histones protect DNA from degradation by exonucleases.
    • Modified histones (e.g., acetylation of H3 and H4) influence chromatin structure and gene expression (activation/inactivation).

    Nucleosome Structure

    • A nucleosome is a fundamental unit of chromatin.
    • It consists of a DNA core wrapped around a histone octamer (2 each of H2A, H2B, H3, and H4).
    • A linker DNA segment joins adjacent nucleosomes.
    • Nucleosomes are linked together by histone H1.

    Chromatin Compaction

    • Chromatin undergoes several levels of compaction.
    • Initially, nucleosomes form a 10-nm fiber.
    • Further compaction results in a 30-nm fiber.
    • The 30-nm fiber forms loops attached to a protein scaffold, creating a rosette structure.
    • Coils of rosettes form chromatids.

    Chromosomes

    • Two identical sister chromatids joined at the centromere constitute a chromosome (during metaphase).
    • The centromere is rich in A-T base pairs, around 130 base pairs long.
    • It has kinetochores, protein complexes that connect to the mitotic spindle and are essential for chromosomal segregation.

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    DNA Structure and Organization PDF

    Description

    Test your knowledge on nucleotides, DNA structure, and their importance in genetics. This quiz covers key concepts including nucleotide composition and the roles of nitrogenous bases in nucleic acids. Gain a deeper understanding of nucleic acids like DNA and RNA through this engaging quiz.

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