Biology: Structure and Location of DNA
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Questions and Answers

What is the main component of chromatin in a non-dividing cell?

  • Only histone proteins
  • RNA and histone proteins
  • DNA and histone proteins
  • DNA, RNA and histone proteins (correct)

    • Approximately how long is the DNA molecule in a human cell?

  • 2 metres (correct)
  • 4 metres
  • 1 metre
  • 3 metres

    • What is the term for the DNA found outside the nucleus in mitochondria and chloroplasts?

  • Intranuclear DNA
  • Extranuclear DNA (correct)
  • Nuclear DNA
  • Mitochondrial DNA

    • What is the shape of the DNA molecule?

    <p>A twisted ladder</p> Signup and view all the answers

    What are the building blocks of DNA?

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

    What is the role of the four nitrogenous bases in DNA?

    <p>They instruct cells on how to synthesise enzymes and other proteins</p> Signup and view all the answers

    What type of bonds hold the sugar and phosphate molecules together in DNA?

    <p>Strong covalent bonds</p> Signup and view all the answers

    What is the rule for the pairing of adenine and thymine in DNA?

    <p>Adenine bonds with thymine or uracil by two hydrogen bonds</p> Signup and view all the answers

    What is the key characteristic that distinguishes purines from pyrimidines?

    <p>Number of rings in their molecular structure</p> Signup and view all the answers

    What is the reason for the genetic code being different between organisms?

    <p>The sequence of nucleotides in their DNA</p> Signup and view all the answers

    What is the primary function of DNA in an organism?

    <p>To carry hereditary information</p> Signup and view all the answers

    What percentage of human DNA codes for proteins?

    <p>Less than 2%</p> Signup and view all the answers

    What is the term for the non-coding regions of DNA?

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

    What is the purpose of DNA replication?

    <p>To ensure the genetic code is passed on from generation to generation</p> Signup and view all the answers

    What is unique about the sequence of nucleotides in identical twins?

    <p>It is identical to each other</p> Signup and view all the answers

    What is the relationship between the complexity of an organism and the amount of non-coding DNA it contains?

    <p>More complex organisms have more non-coding DNA</p> Signup and view all the answers

    Study Notes

    Where is DNA Found?

    • DNA is mainly found in the nucleus of a cell, forming part of the chromatin network.
    • Small amounts of DNA are also found outside the nucleus in mitochondria and chloroplasts, known as extranuclear DNA.

    Structure of DNA

    • DNA is a long, twisted ladder-like molecule that forms a stable, 3-dimensional double helix.
    • The DNA molecule is made up of nucleotides, which are building blocks consisting of a sugar molecule, a phosphate molecule, and a nitrogenous base.

    Nucleotides

    • There are four types of nitrogenous bases: adenine (A), thymine (T), guanine (G), and cytosine (C).
    • These four bases are the foundation of the genetic code, instructing cells on how to synthesize enzymes and other proteins.

    Double Helix Structure

    • The outer two strands of the ladder are formed by a chain of alternating sugar and phosphate links.
    • The rungs of the ladder are formed from pairs of bases linked by weak hydrogen bonds.
    • The base pairs are attached to the sugar molecules.

    Base Pairing

    • Adenine (A) pairs with thymine (T) or uracil (U) using two hydrogen bonds.
    • Cytosine (C) pairs with guanine (G) using three hydrogen bonds.

    Classification of Nitrogenous Bases

    • There are two groups of nitrogenous bases: purines and pyrimidines.
    • Purines consist of two fused rings of nitrogen, carbon, and hydrogen atoms (e.g. guanine and adenine).
    • Pyrimidines consist of one ring of similar atoms and are smaller than purines (e.g. cytosine and uracil).

    Universality of DNA

    • The four nucleotides are the same in all animals and plants.

    Genetic Code

    • The sequence of nucleotides determines the genetic code of an organism.
    • The sequence of nucleotides in certain sections of DNA in a human is different from the same sections in every other human being (except in identical twins).

    Role of DNA

    • DNA molecules carry hereditary information in the form of genes.
    • DNA provides a blueprint for an organism's growth and development by coding for protein synthesis.
    • DNA can replicate, making a copy of itself to pass on genetic information to each daughter cell during cell division.

    Non-Coding DNA

    • Less than 2% of human DNA codes for proteins; the rest consists of non-coding DNA.
    • Non-coding regions are interrupted by protein-coding regions called exons.
    • Complex organisms contain more non-coding DNA than less complex organisms.

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    Description

    Learn about the location of DNA in a cell, its structure, and how it fits inside the nucleus. Discover the composition of chromatin and the length of DNA in a human cell.

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