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Published byBarnaby Lang Modified over 8 years ago
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Aim: How do your genetics play a role in the person you are today? Do Now: What similarities do you have with your parents or siblings? Homework:Textbook 126-132 #1-5
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Human Genetics
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What is Heredity? The transfer of characteristics from one generation to the next
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What are Traits? A characteristic that is determined by your genes A pair of genes will determine the trait Examples: Tongue rolling Earlobes Widow’s Peak Hair Whorl Dimples
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What is genetics? The science of how traits are inherited
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Where do our genes come from? We had said that a pair of genes determines which traits we will inherit from our parents Why would it be a pair of genes? Each parent provides a sex cell in order for fertilization to occur The father will provide a sperm cell that has 23 chromosomes The mother will provide an egg cell that has 23 chromosomes When these two cells merge and become one, fertilization has occurred, and as a result, the new fertilized egg has 46 chromosomes (23 + 23 = 46)
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23 chromosomes + 46 chromosomes 23 chromosomes
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How are traits determined? Dominant Genes – the traits that will usually appear in the individual (represented by an uppercase letter) If an organism has a gene for blue or brown eyes, usually it will have brown eyes because in is the dominant gene Recessive Genes – The gene hidden by the dominant gene (represented by a lowercase letter) Blue-eyed people need two recessive genes to show the blue-eyed trait
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Who is Gregor Mendel? “Father of Genetics” Studied pea plants He crossed pea plants with different characteristics and studied their offspring He was able to determine how traits get passed on from generation to generation
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What is a Punnett Square? A table that shows the possible results when the genes of two parents are crossed It shows the probability of a trait to be expressed in the offspring BB BBBBB bBbBb B – Brown Eyes b – Blue Eyes
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What is a genotype? The genetic code or make up of the individual Examples: BB, Bb, bb
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What is a genotype? Homozygous dominant – a pair of dominant genes (BB) – a pair of dominant genes (BB) Homozygous recessive – a pair of recessive genes (bb) Heterozygous or hybrid – a mixed pair of one dominant gene and one recessive gene (Bb)
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What is a phenotype? The way an organism looks or behaves Examples: GenotypePhenotype BB Brown Hair Bb
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Lets try some Punnett Squares! Examples: Examples: BB x bb Bb x bb Bb x Bb bb x bb BB x BB BB x Bb B = Brown Eyes b = Blue Eyes What we are looking for: 1.Genotypes 2.Phenotypes 3.Percentage Brown eyes 4.Percentage Blue Eyes
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