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Genetics and Inheritance. Genetics: the scientific study of heredity Genetics: the scientific study of heredity People in the 1770s believed that traits.

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Presentation on theme: "Genetics and Inheritance. Genetics: the scientific study of heredity Genetics: the scientific study of heredity People in the 1770s believed that traits."— Presentation transcript:

1 Genetics and Inheritance

2 Genetics: the scientific study of heredity Genetics: the scientific study of heredity People in the 1770s believed that traits blended People in the 1770s believed that traits blended Most of the leading scientists in the 19th century accepted this "blending theory." Most of the leading scientists in the 19th century accepted this "blending theory."

3 Lemarks Idea The inheritance of acquired characteristics. Until the late nineteenth century, people believed that acquired traits were passed down. The inheritance of acquired characteristics. Until the late nineteenth century, people believed that acquired traits were passed down. Tattoos, body building, accidents. Tattoos, body building, accidents. The giraffes long neck is NOT an acquired trait. The giraffes long neck is NOT an acquired trait.

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6 Gregor Mendel Studied to be a monk in Austria in mid 19 th century. Studied to be a monk in Austria in mid 19 th century. Influenced by society to become a noble person – a person of God. Influenced by society to become a noble person – a person of God. Mendel loved science, and to pass time – he took care of the garden. Fell in love with it. Mendel loved science, and to pass time – he took care of the garden. Fell in love with it. Began to notice certain similar characteristics. Began to notice certain similar characteristics.

7 More Mendel… He observed multiple generations of pea plants, and noticed subtle changes – and wondered why they occurred. He observed multiple generations of pea plants, and noticed subtle changes – and wondered why they occurred. He collected data for years and began to formulate hypotheses. He collected data for years and began to formulate hypotheses.

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9 Mendel picked common garden pea plants for the focus of his research because they: Mendel picked common garden pea plants for the focus of his research because they: –can be grown easily in large numbers – reproduction can be manipulated. – reproduction can be manipulated. –Pea plants have both male and female reproductive organs. As a result, they can either self-pollinate themselves or cross-pollinate with another plant. –Pea plants have both male and female reproductive organs. As a result, they can either self-pollinate themselves or cross-pollinate with another plant.

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12 Mendel observed seven traits that are easily recognized and apparently only occur in one of two forms: Mendel observed seven traits that are easily recognized and apparently only occur in one of two forms: 1. flower color is purple or white 1. flower color is purple or white 2. seed color is yellow or green 2. seed color is yellow or green 3.flower position is axil or terminal 3.flower position is axil or terminal 4.pod shape is inflated or constricted 4.pod shape is inflated or constricted 5.stem length is long or short 5.stem length is long or short 6.pod color is yellow or green 6.pod color is yellow or green 7.seed shape is round or wrinkled 7.seed shape is round or wrinkled

13 Mendels Experiment The key to his experiment was that he started with pure breed plants. The key to his experiment was that he started with pure breed plants. Pure breed means that they contain only one type of gene – YY Pure breed means that they contain only one type of gene – YY Allele – different versions of the same gene. Allele – different versions of the same gene.

14 Mendels Experiment Continued…. In cross-pollinating – he crossed yellow and green seeds In cross-pollinating – he crossed yellow and green seeds Mendel found that the first offspring generation (F1) produced ALL yellow peas. Mendel found that the first offspring generation (F1) produced ALL yellow peas.

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16 Results of F2 After he obtained the F1 offspring, he self – pollinated a yellow seeded plant with itself. After he obtained the F1 offspring, he self – pollinated a yellow seeded plant with itself. The results (F2 generation) had a 3:1 ratio – 3 yellow and 1 green. The results (F2 generation) had a 3:1 ratio – 3 yellow and 1 green.

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18 Mendel continued this practice 28,000 times over about years with different traits. Mendel continued this practice 28,000 times over about years with different traits. Mendel came up with 2 fundamental laws. Mendel came up with 2 fundamental laws.

19 Mendels Laws Law of Independent Assortment – each trait is found on separate genes and each gene comes in pairs that will separate on their own. Law of Independent Assortment – each trait is found on separate genes and each gene comes in pairs that will separate on their own. Law of Segregation - TBTAALD Law of Segregation - TBTAALD

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21 Mendel's Theory Mendel's Theory Mendel's Theory –Each individual has two factors (we now call these genes) for each trait. –When both genes are the same, the individual is said to be homozygous for that trait. If the two genes are different, the individual is heterozygous for that trait. –Alternate types of genes for each trait are alleles. –The actual genetic makeup of an individual is the genotype. Phenotype refers to the outward expression of the genes.

22 What Did Mendell gather from his Data What Did Mendell gather from his Data 2 big Laws 2 big Laws Mendel's First Law: Law of Segregation, says that only one allele is passed to a gamete, and gametes join randomly when uniting to form offspring. Mendel's First Law: Law of Segregation, says that only one allele is passed to a gamete, and gametes join randomly when uniting to form offspring.

23 Mendel's Second Law: Law of Independent Assortment Mendel's Second Law: Law of Independent Assortment

24 Analyzing Mendel's Results Punnett Squares - an easy way to express the probabilies of genotypes Punnett Squares - an easy way to express the probabilies of genotypes

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29 A dihybrid cross involves a study of inheritance patterns for organisms differing in two traits. A dihybrid cross involves a study of inheritance patterns for organisms differing in two traits. Mendel invented the dihybrid cross to determine if different traits of pea plants, such as flower color and seed shape, were inherited independently. Mendel invented the dihybrid cross to determine if different traits of pea plants, such as flower color and seed shape, were inherited independently. in a dihybrid cross that led Mendel to propose that alleles of different genes are assorted independently of one another during the formation of gametes. in a dihybrid cross that led Mendel to propose that alleles of different genes are assorted independently of one another during the formation of gametes.

30 Punnet Square for Dihybrid Cross Punnet Square for Dihybrid Cross S=smooth seed S=smooth seed s=dented seed s=dented seed Y=yellow Y=yellow Y=green Y=green

31 Heterozygous smooth seed plant that is also heterozygous yellow seeded plant Heterozygous smooth seed plant that is also heterozygous yellow seeded plant Heterozygous smooth seed plant that is also heterozygous yellow seeded plant is mated with Heterozygous smooth seed plant that is also heterozygous yellow seeded plant is mated with

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34 Smooth, yellow phenotype Smooth, yellow phenotype

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36 Smooth, green phenotype Smooth, green phenotype

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38 Dented, yellow phenotype Dented, yellow phenotype

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40 Dented, green phenotype Dented, green phenotype

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