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What is the Secret of Life? Deoxyribonucleic Acid is the Answer History Lesson on DNA 1869 Swiss scientist Friedrich Miescher collected bloodied bandages at the local hospital Collected nuclei from cells found on the bandages

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What is the Secret of Life?

Deoxyribonucleic Acid is the Answer


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History Lesson on DNA

  • 1869

  • Swiss scientist Friedrich Miescher collected bloodied bandages at the local hospital

    • Collected nuclei from cells found on the bandages

    • Isolated a substance called NUCLEIN - this is the first time that DNA was isolated

    • Unfortunately, he didn’t know anything else about this molecule


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History Lesson on DNA

  • 1944

  • Canadian Scientist Oswald Avery proposed that DNA was involved in HEREDITY (the passing of traits down from parent to offspring)


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History Lesson on DNA

  • 1953

  • British Scientists James Watson and Francis Crick reveal the structure of DNA

  • Perhaps the most important scientific discovery of the century


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Structure of DNA

  • Watson and Crick described the structure of DNA as a “double helix” – in simple terms, it looks like a coiled ladder

    • Sides of ladder – made of alternating sugars and phosphates

    • Rungs of ladder – made of four chemicals called nitrogen bases



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Nitrogen Bases

  • There are only four nitrogen bases that make up a molecule of DNA

    • Adenine (abbreviated as A)

    • Cytosine (abbreviated as C)

    • Guanine (abbreviated as G)

    • Thymine (abbreviated as T)

  • The secret of life is contained in the order of these four nitrogen bases on a DNA molecule – GENETIC CODE

    • This code instructs cells what structures every cell in an organisms’ body should produce


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The Genetic Code

  • The code is like a blueprint that controls the production of proteins in the cell

  • Proteins makes up a lot of structures in animals and plants

  • Airlines use three letter codes for airports around the world

    • YYC – Calgary

    • YYZ – Toronto

    • YVR – Vancouver

    • LAX – Los Angeles

  • Each section of DNA will code for a specific part of a protein – just like airlines


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Nitrogen Bases

  • Remember that a DNA molecule is a double helix

  • Certain nitrogen bases are compatible only with each other

    • Adenine (A) will only pair with Thymine (T)

    • Cytosine (C) will only pair with Guanine (G)


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How does DNA fit into the nucleus of a cell?

  • There is a lot of DNA in a nucleus (about 2 meters of it)

  • To make it fit, it is tightly coiled in little packages called CHROMOSOMES

    • In human cells – 46 chromosomes

      • Chromosomes are found in pairs (23 pairs in humans)

      • Offspring get one set of chromosomes from their mother and one set from their father

    • All cells (except for gametes) will have 46 chromosomes in their nuclei (GAMETES will have only half or 23 chromosomes)


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Chromosomes of other Organisms

  • Humans have 46 chromosomes but not all species have that number

    • Gorilla - 48 chromosomes (24 pairs)

    • Fruit Fly – 8 chromosomes (4 pairs)

    • Sheep – 54 chromosomes (27 pairs)

    • Dog – 78 chromosomes (39 pairs)

    • Cat – 38 chromosomes (19 pairs)

    • Horse – 64 chromosomes (32 pairs)

  • Even though all of these species have different numbers of chromosomes – the DNA is still made up of A, C, G, and T – just in a different order


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What happens when there are a different number of chromosomes in a cell?

  • Normal human cells have 46 chromosomes, however during reproduction, problems can occur causing fewer or more chromosomes being present


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Down’s Syndrome chromosomes in a cell?

  • 47 chromosomes – 3 copies of chromosome number 21 in humans

    • Mental retardation

    • Extra fold of skin on eyelids

    • A flattened forehead

    • Poor muscle development


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Down’s Syndrome chromosomes in a cell?

www.einstein-syndrome.com/ house/evan_stories.htm


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Turner’s Syndrome chromosomes in a cell?

  • 45 chromosomes – only 1 X chromosome (normal females have 2 X chromosomes and normal males have 1 X and 1 Y chromosome)

    • Sterile

    • Short stature


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Turner’s Syndrome chromosomes in a cell?Karyotype of a patient with the syndrome


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XYY “Super Male” chromosomes in a cell?

  • 47 chromosomes – males that have 2 Y chromosomes (normal males only have 1 Y chromosome)

    • Used to be thought to be a cause of violent behaviour


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Klinefelter’s Syndrome chromosomes in a cell?

  • 47 chromosomes – males have an extra X chromosomes

    • Small testicles

    • Sterile

    • Frequent mental retardation


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Genes are found on Chromosomes chromosomes in a cell?

  • Genes are segments of DNA containing coded instructions for the formation of structures

  • Humans have 30,000 genes on 23 pairs of chromosomes within every cell’s nucleus


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Characteristics of Genes chromosomes in a cell?

  • Genes are located on chromosomes in nuclei

  • Each chromosome has a number of genes located on it

  • Genes, like chromosomes, come in pairs

  • Both genes in a pair carry DNA instructions for the same thing, and they occupy matching locations on the two chromosomes

  • Offspring inherit genes from both parents, however the genes may be in different forms (ALLELES)


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Chromosomes, Genes and Alleles chromosomes in a cell?


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