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Heredity The passing of traits from parents to offspring The traits you have resemble your parents These traits can include ◦ Eye color ◦ Shape of Eyes ◦ Color of your hair ◦ Height
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Gregor Mendel Mendel: Austrian Monk, Father of Genetics Genetics- branch of biology focusing on heredity Crossed pea plants, counted offspring, analyzed data
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Why are pea plants useful for genetics? 1. Traits exist in 2 opposing forms, without intermediates 2. Have male and female organs Easily control mating (self- fertilization or cross- pollination) 3. Small, grow easily and quickly, produce many offspring
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Monohybri d Cross Monohybrid Cross: Involves one pair of contrasting traits For Example: ◦ Crossing a plant with purple flowers and a plant with white flowers
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True Breeding Step 1: Mendel wanted to create a “Parental generation” also called the “P” generation True Breeding: Self pollinated pea plants so all the offspring would display only one form of the trait Ex: A purple flowering plant only produces purple flowers Why would this be important?
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Mendel’s Study of Traits – Step 2 F1 Generatio n Step 2: Cross pollinated two P generation plants (Purple and White flowers) Called the offspring from the P generation the F 1 generation (First) Results: All were purple flowers
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F2 Generation Step 3: The F 1 Generation self pollinated. The offspring from the F 1 generation was called the F 2 generation Results: Three purple flowers, one white flower
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What were the results of the F 1 Generation? What were the results of the F 2 generation? What should Mendel’s conclusion be?
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Give one reason why pea plants are good subjects for genetic experiments Why was it important that Mendel performed true breeding for the P generation? What did Mendal call each generation?
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Mendel’s Hypotheses 1. Individuals inherit 2 copies of each gene (trait)- one from each parent ◦ Gametes carry only one allele for each inherited trait 2. Alleles- different contrasting versions of each gene (one from each parent) Ex: Brown eyes vs. Blue eyes
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Mendel’s Hypothese s 3. When 2 different alleles are present the Dominant one is expressed 4. Recessive- trait that’s not expressed when the dominant allele is present
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Genetics Terms In the following gentoype which letter represents the dominate gene? Which letter represents the recessive gene?
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Genetics Terms Homozygous- 2 alleles of a gene are the same (PP or pp) Heterozygous- if the 2 alleles for a gene are different (Pp) ◦ Only the dominant allele is expressed (masks the recessive allele)
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Genetics Terms Genotype- allele combinations (genes) ◦ Ff- Heterozygous ◦ FF- Homozygous dominant ◦ ff- Homozygous recessive Phenotype: is the physical appearance of the trait Ex: If “B” equals brown eyes and the genotype is Bb the phenotype (expressed trait) would be Brown eyes
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Whiteboards – Quick Questions What would be the genotype for an individual heterozygous for the “F” trait? Ff What would be the phenotype for an individual whose genotype is Tt where T is tall and t is short? Tall
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Whiteboards – Quick Questions Give an example of a heterozygous trait Ex: Ff Give an example of a homozygous trait Ex: FF, ff What would be the genotype for an individual heterozygous for the “F” trait? Ff What would be the phenotype for an individual whose genotype is Tt where T is tall and t is short? Tall
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Laws of Heredity Law of segregati on 1. Law of Segregation: Allele’s separate during meiosis to produce gametes F 1 generation (zygote) has allele’s for each trait by both parents
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Law of Independent Assortment 2. Law of Independent Assortment: Alleles of genes separate independently of one another during gamete formation Ex: Alleles for plant height separate independently of the alleles for flower color Results: The inheritance of one trait does not influence the inheritance of another – COMPLETELY SEPARATE
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What is the Law of Segregation? What is the Law of Independent Assortment? Identify the phenotypes of rabbits with the genotypes Bb and bb, where B- black coat and b- brown coat.
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