Human Genetics and Molecular Biology Overview
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Questions and Answers

What is the direction of helical rotation for A-DNA?

  • Counterclockwise
  • Undefined
  • Right (correct)
  • Left

    • Which form of DNA is most prevalent within cells?

  • A-DNA
  • Z-DNA
  • B-DNA (correct)
  • Supercoiled DNA

    • What type of groove in DNA acts as a binding site for regulatory proteins?

  • Narrow groove
  • Flat groove
  • Minor groove
  • Major groove (correct)

    • What is the number of residues per turn of helix in Z-DNA?

    <p>12 base pairs</p> Signup and view all the answers

    Where is DNA located in eukaryotic cells?

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

    Which class of DNA-binding proteins is primarily involved in chromatin structure?

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

    Which of the following best describes the primary function of DNA?

    <p>To transmit genetic information</p> Signup and view all the answers

    Histones are rich in which types of amino acids?

    <p>Basic amino acids</p> Signup and view all the answers

    Which form of DNA has a flat major groove?

    <p>Z-DNA</p> Signup and view all the answers

    What type of structure do purines have?

    <p>Double ring structure</p> Signup and view all the answers

    Which nitrogenous base is found only in RNA?

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

    Which statement about histones is true?

    <p>They protect DNA from digestion by exonucleases.</p> Signup and view all the answers

    What is the role of the phosphate group in a nucleotide?

    <p>To link nucleotides together</p> Signup and view all the answers

    Which component distinguishes DNA from RNA?

    <p>5-carbon sugar</p> Signup and view all the answers

    Which of the following is NOT a purine?

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

    What is the polymer of DNA composed of?

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

    What is formed when a base is covalently linked to the number 1 carbon of a sugar?

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

    Which bond is involved in the linkage of phosphate groups to the 5′ carbon of a nucleoside?

    <p>Phospho-ester bond</p> Signup and view all the answers

    What does the primary structure of DNA refer to?

    <p>The sequence of bases in the nucleic acid chain</p> Signup and view all the answers

    In the secondary structure of DNA, which base pairs with thymine (T)?

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

    What is the nature of the two strands of DNA in the double helix?

    <p>Antiparallel to each other</p> Signup and view all the answers

    Which of the following forms a high-energy compound?

    <p>Nucleoside triphosphate</p> Signup and view all the answers

    What structural form describes the winding of two DNA strands around each other?

    <p>B-form double helix</p> Signup and view all the answers

    What type of bond connects nucleotides in a DNA strand?

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

    What indicates a deviation from Chargaff’s rules in nucleic acid analysis?

    <p>The presence of single-stranded nucleic acid</p> Signup and view all the answers

    Which of the following types of histone molecules is not commonly found in nature?

    <p>H3</p> Signup and view all the answers

    What type of disease inheritance pattern is NOT associated with mutations in mitochondrial DNA?

    <p>Paternal pattern of diseases</p> Signup and view all the answers

    Which chromosome structure would be degraded first in an apoptotic cell?

    <p>10-nm fibre</p> Signup and view all the answers

    Which factor does NOT increase the melting temperature of DNA?

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

    What is the basic packaging unit of chromatin?

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

    What is the length of DNA that forms the nucleosome core?

    <p>140-150 base pairs</p> Signup and view all the answers

    What type of chromatin is more transcriptionally active?

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

    What is the size of the chromosome when fully condensed?

    <p>1400 nm</p> Signup and view all the answers

    How many histones are typically present in a nucleosome core?

    <p>8</p> Signup and view all the answers

    What type of DNA structure do eukaryotic nuclear chromosomes have?

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

    What is the characteristic of heterochromatin?

    <p>Gene poor</p> Signup and view all the answers

    What is the length of mitochondrial DNA?

    <p>16 kb</p> Signup and view all the answers

    What process separates double-stranded DNA into single strands?

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

    Which condition does NOT contribute to the denaturation of DNA?

    <p>Presence of salt</p> Signup and view all the answers

    What is the melting temperature (Tm) of DNA?

    <p>The temperature at which DNA exists as single strands</p> Signup and view all the answers

    What characteristic affects the melting temperature (Tm) of DNA?

    <p>Base composition</p> Signup and view all the answers

    What type of enzyme removes nucleotides from the ends of a nucleic acid?

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

    Which of the following nucleotides is NOT found in DNA?

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

    How many hydrogen bonds are formed between guanine and cytosine in DNA?

    <p>3 hydrogen bonds</p> Signup and view all the answers

    In B-form DNA, what is the width of the double helix in nanometers?

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

    Study Notes

    Human Genetics and Molecular Biology

    • This presentation focuses on DNA, its structure, function, and associated concepts.

    DNA Site

    • Eukaryotes: DNA is located inside the nucleus and mitochondria.
    • Prokaryotes: DNA is in the cytoplasm and often exists as non-chromosomal DNA (plasmids).

    DNA Function

    • Storing genetic information: transmitted to the next generation through replication.
    • Controlling protein synthesis: enabling cells to perform their functions via transcription and translation.

    DNA & Nucleotide Structure

    • DNA is a polymer of deoxynucleotides linked by phosphodiester bonds.
    • Each nucleotide comprises:
      • A nitrogenous base (purine or pyrimidine).
      • A 5-carbon sugar (deoxy-pentose).
      • Phosphate.
    • Purines: Adenine (A) and Guanine (G).
    • Pyrimidines: Cytosine (C), Thymine (T), and Uracil (U).
      • Thymine is primarily in DNA, while uracil is in RNA.

    Pentose Sugar

    • Deoxyribose is the sugar in DNA.
    • Ribose is the sugar in RNA.

    Phosphate

    • One or more phosphate groups attach to the 5' carbon of the pentose sugar.

    Nucleosides and Nucleotides

    • Nucleosides: formed by covalently linking a base to the 1' carbon of a sugar (N-glycosidic bond).
    • Nucleotides: formed by attaching one or more phosphate groups to the 5' carbon of a nucleoside (phospho-ester bond).

    DNA Structure

    • Primary structure: sequence of bases in the nucleic acid chain of DNA.
      • DNA is composed of nucleotides (dNTPs).
      • Nucleotides are connected by phosphodiester bonds.
      • The strand has a 5' end with a phosphate group and a 3' end with a hydroxyl group.
    • Secondary structure: double-stranded DNA, with A pairing with T and G pairing with C(Chargaff's rule), forming a double helix in antiparallel orientation 5'->3' and 3'->5'.
    • Tertiary structure: Chromatin structure in which DNA interacts with DNA-binding proteins (histones and non-histones) to form a compact structure.

    Chromatin Structure

    • Chromatin is a complex of DNA and proteins.
    • Two classes of DNA-binding proteins (histones): histones and non-histones.
      • Histones: positively charged, forming ionic bonds with the negatively charged DNA. Their main function is to compact the DNA.
      • Non-histones: involved in regulating the structure and function of chromatin.
    • Nucleosome: the basic packaging unit of chromatin.
      • The nucleosome comprises:
        • DNA core: 140-150 base pairs of DNA wrapped around 8 histone proteins (2 each of H2A, H2B, H3, and H4).
        • Linker DNA: 20-200 base pairs connecting the nucleosomes.
    • Chromatin structure:
      • Nucleosomes (beads on a string), coiled into 30 nm chromatin fiber, forming loops, culminating in chromatin fibers, leading to the chromosome structure that is evident in metaphase

    Heterochromatin and Euchromatin

    • Heterochromatin: more compact, less active regions of DNA, and usually gene-poor (AT rich).
    • Euchromatin: less compact, more active, and gene-rich (GC rich). Euchromatin is susceptible to nuclease digestion.

    Types of DNA

    • Double-stranded linear: eukaryotic nuclear chromosomes.
    • Double-stranded circular: mitochondrial, bacterial, plasmid, viral, and chloroplast DNA.
    • Single-stranded circular: small viruses.

    Mitochondrial DNA

    • Circular double-stranded DNA molecule (approximately 16 kb).
    • Encodes for several genes involved in energy production.
    • Higher mutation rate than nuclear DNA.
    • Inherited maternally.

    Denaturation/Renaturation of DNA

    • Denaturation (melting): unwinding of double-stranded DNA to single strands. Factors that cause denaturation include heat, alkaline pH, and chemicals like formamide and urea.
    • Renaturation (reannealing): re-formation of double-stranded DNA from separated single strands. This occurs when the denaturing conditions are gradually reduced.
    • Melting temperature (Tm): the temperature at which 50% of the DNA molecules are in their single-stranded state. Tm is higher for DNA regions with more G-C pairs than A-T pairs.

    Nucleases

    • Exonucleases: enzymes that remove nucleotides from the ends (5' or 3') of DNA.
    • Endonucleases: enzymes that cut DNA within the molecule.

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    BIOL 101 1 DNA - Human Genetics and Molecular Biology PDF

    Description

    This quiz explores key concepts related to DNA, including its structure, function, and location in eukaryotic and prokaryotic cells. It delves into the functions of DNA in genetic information storage and protein synthesis, as well as the composition of nucleotides. Test your understanding of these fundamental aspects of molecular biology.

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