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Changes in DNAcan produce variation
Section 5.2
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DNA sequence can change
• Differences in DNA are what make one organism different from another
• The number of differences between two species is large
Human3 billion
Base pairs
Yeast cell12 MillionBase Pairs
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DNA sequence can change
• The number of differences between 2 individuals of the same species is small
• (<0.1% variation)
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DNA sequence can change
• There is a large number of DNA bases in any organism that need to be copied
• Errors can occur when DNA is copied or affected by environment– UV radiation– X-rays– Toxins
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DNA sequence can change
• Mutation – any change in DNA• Cells have ways of fixing mistakes in DNA• However some mistakes are not fixed
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Possible outcomes when error occurs in genes
No effect – Some amino acids have more than one code and may not change resulting protein
– May have enough protein being produced
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Possible outcomes when error occurs in genes
• Mutation is minor– May only cause a change in appearance
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Possible outcomes when error occurs in genes
Mutation is great– Could be good (Resistant to disease)
– Could be bad (genetic disorder or disease)
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• Only 5% of human DNA is in genes
• If mutation occurs in a non-coding region, then chances are that the mutation is neutral
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Genetic Disorders
• Disease or condition caused by mutations that affect normal functions of the cell– Can be inherited (Tay-Sachs)– Can occur during a person’s life (Cancer)
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Genetic Disorders• A person can carry a tendency for a disease
(diabetes)
• Sometimes a person’s behavior can prevent the disease (smoking)
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Genetic Disorders
• Mutations can have more than one effect– Sickle cell anemia• Recessive disorder• Prevents blood from carrying oxygen• Prevents malaria
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Genetic Disorders
• Pedigree – shows a family relationship for 2 or more generations
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Cancer
• A group of disorders• Characterized by uncontrolled division of cells• Cells can spread to other tissues• Causes– Inherited– Carcinogens– Radiation– Series of mutations
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