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1
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2
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- The nucleus of a human cell contains between 30 000 and 40 000
genes. This complete set of genes is called the GENOME.
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3
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4
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- Tightly coiled threads of deoxyribonucleic acid (DNA) and associated
protein molecules
- Organized into structures called chromosomes
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5
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6
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- A packet of coiled up DNA
- Humans have 23 pairs of chromosomes
- They are in the nucleus of cells
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7
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- Chromosomes contain a single, long piece of DNA
- A chromosome is about 0.004 mm long
- The DNA is about 4 cm long
- This is about 10 000 times longer than the chromosome
- So it has to twist and coil to fit inside
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8
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- There are 23 pairs of chromosomes in the nucleus of any one of your
cells
- Each chromosome has a single strand of DNA (deoxyribonucleic acid) which
carries the code for a couple of thousand genes
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9
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10
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- A code made up of pairs of bases carried on the DNA molecule.
- Each DNA molecule contains many genes
- The basic physical and functional units of heredity
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11
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- A specific sequence of bases
- Sequences carry the information needed for constructing proteins
- Proteins provide the structural components of cells and tissues as
well as enzymes for essential biochemical reactions.
- The human genome is estimated to be made of more than 30,000 genes.
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12
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- Each chromosome carries a couple of thousand genes
- Many of these are common to all human beings.
- So, 99.9% of your DNA is identical to everyone else's
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13
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- The remaining 0.1% influences the differences between us
- height, hair color and susceptibility to a particular disease
- Environmental factors, such as lifestyle (for example, smoking and
nutrition) also influence the way we look and our susceptibility to
disease
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14
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15
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- The DNA molecule is made from two strands, twisted together in a double helix.
- The links between each strand are called bases.
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16
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- Deoxyribonucleic acid
- The molecule that contains the genetic code
- It coils up tightly inside chromosomes
- DNA is a double helix made from
two strands which are joined together by a pair of bases
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17
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18
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19
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20
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21
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- Two strands that wrap around each other to resemble a twisted ladder
whose sides
- Made of sugar and phosphate molecules
- Connected by rungs of nitrogen- containing chemicals called bases
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22
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23
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24
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- Nitrogen- containing chemicals
- The parts of the DNA molecule that join the two helix strands
- They are like rungs on a ladder
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25
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- There are four bases: adenine (A), thymine (T), guanine (G) and cytosine
(C)
- Each base can only join with one other base
- they join together in pairs: A with T and G with C.
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26
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- The particular order of the bases is called the DNA sequence
- The sequence gives the exact genetic instructions needed to create a
particular organism with its own unique traits.
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Notes
