DNA, Chromosomes & Human Genome
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Questions and Answers

What is a characteristic of tandem repeat DNA?

  • It includes sequences that are not clustered.
  • It makes up the majority of mitochondrial DNA.
  • It consists of short nucleotide repeats. (correct)
  • It is dispersed throughout the genome.

    • Which of the following best describes the mitochondrial genome?

  • Circular double-stranded DNA. (correct)
  • Contains no genes and is non-functional.
  • Linear and larger than nuclear DNA.
  • Completely packaged into chromatin.

    • What is the primary function of mitochondrial DNA?

  • To store genetic information exclusively.
  • To facilitate Mendelian inheritance.
  • To replicate the nuclear DNA.
  • To produce enzymes required for oxidative phosphorylation. (correct)

    • Which of the following correctly describes the inheritance pattern of mitochondrial DNA?

    <p>Exclusively maternal inheritance. (C)</p> Signup and view all the answers

    Which type of DNA is primarily used for DNA fingerprinting?

    <p>Short tandem repeats (STRs). (B)</p> Signup and view all the answers

    What is the shape of nucleosomes in DNA packaging?

    <p>Beads on a string (B)</p> Signup and view all the answers

    How many nucleosomes are there in a single turn of the solenoid structure?

    <p>6 (B)</p> Signup and view all the answers

    What is the approximate thickness of chromatid in DNA packaging?

    <p>700 nm (D)</p> Signup and view all the answers

    In a diploid organism, how many chromosomes are typically found in a human somatic cell?

    <p>46 (A)</p> Signup and view all the answers

    Which histone protein is NOT part of the nucleosome core?

    <p>H1 (C)</p> Signup and view all the answers

    What is the term for the structure formed by the loops of chromatin fibers binding to non-histone scaffold proteins?

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

    During which phase can chromosomes, containing complexed DNA and protein, be observed under a microscope?

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

    What structure is described as having a thickness of 30 nm in the DNA packaging hierarchy?

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

    What is the total number of chromosomes found in human somatic cells?

    <p>46 (A)</p> Signup and view all the answers

    Which sex chromosome combination is typical for a human female?

    <p>Two X chromosomes (D)</p> Signup and view all the answers

    What does the term 'homologous chromosomes' refer to?

    <p>Chromosome pairs carrying matching genetic information (B)</p> Signup and view all the answers

    What is the primary function of repetitive DNA sequences?

    <p>Maintaining chromosome structure (D)</p> Signup and view all the answers

    How are chromosomes identified based on centromere position?

    <p>By categorizing into metacentric, submetacentric, and acrocentric (C)</p> Signup and view all the answers

    What is the size of the human nuclear genome?

    <p>3.1 Gb (C)</p> Signup and view all the answers

    What percentage of the human genome is made up of protein-coding sequences?

    <p>1.5% (B)</p> Signup and view all the answers

    What characteristic of chromosome 22 differs from what is usually expected based on chromosome length?

    <p>It is longer than chromosome 21 (A)</p> Signup and view all the answers

    What type of bond connects the nitrogenous bases in DNA?

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

    Which deoxyribonucleic acid (DNA) component is attached to the 1' carbon of the deoxyribose sugar?

    <p>Nitrogenous base (C)</p> Signup and view all the answers

    What structure is formed when DNA is coiled and associated with proteins?

    <p>Chromatin (C)</p> Signup and view all the answers

    What describes the orientation of the two strands in a DNA double helix?

    <p>Anti-parallel configuration (D)</p> Signup and view all the answers

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

    <p>To carry genetic information (C)</p> Signup and view all the answers

    What is the term for the bond formed between the deoxyribose sugar of one nucleotide and the phosphate of another?

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

    Which base pairs with adenine in DNA?

    <p>Thymine (C)</p> Signup and view all the answers

    What is the significance of the 5’ and 3’ ends of a DNA strand?

    <p>They determine the direction of DNA replication. (C)</p> Signup and view all the answers

    Flashcards

    Genetic Material

    DNA is the primary carrier of genetic information, a chain of nucleotides.

    Nucleotide

    The building block of DNA, composed of a sugar, a phosphate group, and a nitrogenous base.

    DNA Structure

    DNA is a double helix, two strands twisted together, held by hydrogen bonds between complementary base pairs (A-T, C-G).

    Base Pairs

    Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

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    DNA Packaging

    DNA coils around proteins and then compacts into chromatin, making it fit inside cells.

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    Chromosome

    A packaged structure of DNA and proteins.

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    Double Helix

    Two strands of DNA twisted around each other in the shape of a spiral.

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    5' and 3' ends

    The ends of a DNA strand marked by the carbons of the sugar component .

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    Somatic Cells

    Body cells with a full set of 46 chromosomes (23 pairs), including 22 pairs of autosomes and 1 pair of sex chromosomes.

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    Gametes

    Reproductive cells (sperm and ova) with half the number of chromosomes (23), containing 22 autosomes and 1 sex chromosome.

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    Autosomes

    Chromosomes responsible for traits other than sex determination. Humans have 22 pairs.

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    Sex Chromosomes

    Chromosomes that determine sex. Females have two X chromosomes, while males have one X and one Y.

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    Homologous Chromosomes

    Pairs of chromosomes that carry matching genetic information. One member is from the father, the other from the mother.

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    Centromere

    The constricted region of a chromosome where spindle fibers attach during cell division.

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    Telomere

    Protective caps at the ends of chromosomes that prevent DNA damage. They shorten with each cell division.

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    Metacentric

    A chromosome where the centromere is located in the middle, resulting in two equal arms.

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    Histone

    A protein that helps package DNA into nucleosomes, providing structural support and regulating gene expression.

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    Linker DNA

    The DNA segment between two nucleosomes, interacting with the H1 histone protein.

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    Solenoid

    A helical structure formed by coiling a nucleosome filament, further compacting the DNA.

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    Looped Domain

    A loop of chromatin fiber, further compacted by binding to scaffold proteins.

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    Chromatid

    A highly compacted structure formed by the further condensation of looped domains, containing a single DNA molecule.

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    Karyotype

    The organized arrangement of chromosomes in a cell, showing the number and appearance of each chromosome.

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    Tandem Repeat DNA

    Short nucleotide repeats clustered together in one or more locations on a chromosome. They contribute significantly to the genetic diversity between individuals.

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    Micro-Satellite DNA

    A type of tandem repeat DNA with very short repeating sequences (1-6 base pairs). Also known as short tandem repeats (STRs) or simple sequence repeats (SSRs).

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    Mini-Satellite DNA

    A type of tandem repeat DNA with longer repeating sequences (10-100 base pairs). Also known as variable number tandem repeats (VNTRs) and commonly used in DNA fingerprinting.

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    Dispersed Repetitive DNA

    Short DNA sequences scattered throughout the genome. These sequences are not clustered like tandem repeats.

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    Mitochondrial DNA (mtDNA)

    A circular, double-stranded DNA molecule present in mitochondria. It contains 37 genes encoding proteins involved in energy production.

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    Study Notes

    DNA, Chromosomes & Human Genome

    • Genetics is the study of the origin, transmission, and expression of genetic information.
    • Medical Genetics is the branch of medicine focusing on inheritance, diagnosis, and treatment of genetically-based diseases.
    • Molecular Genetics studies the structure and function of genes at a molecular level.
    • Cytogenetics studies chromosomes, their structure, and inheritance.

    What is the Genetic Material?

    • The genetic material is DNA.
    • DNA is arranged in structures called chromosomes.

    DNA

    • DNA is a double helix composed of nucleotides.
    • Nucleotides have a phosphate group, a sugar, and a nitrogenous base.
    • The sugar in DNA is deoxyribose.
    • The nitrogenous bases are adenine (A), thymine (T), guanine (G), and cytosine (C).
    • A pairs with T, and G pairs with C.
    • The strands are anti-parallel.
    • DNA is usually found in the nucleus of eukaryotic cells.
    • DNA in a cell is referred to as the genome.

    DNA Packaging

    • DNA is associated with proteins (histones), coiled to form chromatin.
    • The fundamental unit of chromatin is the nucleosome.
    • Nucleosomes consist of DNA wrapped around a core of histone proteins.
    • DNA forms a filament (11nm).
    • The nucleosome filament coils into a solenoid (~30nm).
    • Loops of chromatin fibers bind to non-histone proteins to form looped domains (~70nm).
    • Looped domains further compact to form the chromatid.
    • The final compact form of DNA is the chromosome (1400nm).

    Chromosomes

    • Chromosomes are rod-shaped structures found in the nucleus.
    • Each chromosome is composed of one double-stranded DNA molecule and protein.
    • Humans have 46 chromosomes in somatic cells.
    • The first 22 pairs of chromosomes (autosomes) are identical in both sexes.
    • The 23rd pair is the sex chromosome; they differ between sexes (XX in females, XY in males).
    • Gametes (sperm and ova) have 23 chromosomes.

    General Organization of Human Genome

    • The human genome is the complete set of genes in a human cell.
    • Human genome contains approximately 20,000–40,000 genes in the nuclear genome.
    • Nuclear DNA makes up 99% of the human genome and is passed on from both parents.
    • Mitochondrial DNA (mtDNA) makes up 1% of the genome. The mtDNA is inherited solely from the mother.
    • mtDNA is circular and contains only 37 genes.

    Nuclear Genome

    • Nuclear genome is linear double-stranded DNA.
    • It occupies 3.1 Gb (~3.1 billion base pairs).
    • Distributed amongst 46 chromosomes (44 autosomes, 2 sex chromosomes).
    • Genes vary in distribution among chromosomes, some are gene dense chromosomes (e.g., 19 & 22), and some are gene poor (e.g., 4 & 18).
    • The Nuclear genome contains single-copy DNA (unique DNA) and repetitive DNA sequences.

    Repetitive DNA Sequences

    • Repetitive DNA includes tandem repeats (e.g., satellite DNA) and dispersed repeats (e.g., SINES and LINES).
    • Tandem repeats are short nucleotide sequences repeated in tandem.
    • Dispersed repeats are scattered throughout the genome.

    Mitochondrial Genome

    • Mitochondrial DNA is circular, double-stranded DNA found in mitochondria.
    • It is ~16kb (~16 thousand base pairs) in size.
    • Inherited only from the mother.
    • Contains 37 genes that encode proteins essential for energy production in the mitochondria.

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    DNA, Chromosomes & Human Genome PDF

    Description

    Explore the fundamental concepts of DNA, chromosomes, and the human genome in this quiz. Learn about the structure of DNA, its role as genetic material, and the various branches of genetics. Test your understanding of molecular genetics and cytogenetics.

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