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Ch. 8 Heredity

Ch. 8 Heredity. GLE 0707.4.3 Explain the relationship among genes, chromosomes, and inherited traits TB 234-240. Explain how traits are inherited Identify Mendel’s role in history of genetics Use Punnett Squares to predict the results of the crosses

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Ch. 8 Heredity

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  1. Ch. 8 Heredity GLE 0707.4.3 Explain the relationship among genes, chromosomes, and inherited traits TB 234-240

  2. Explain how traits are inherited • Identify Mendel’s role in history of genetics • Use Punnett Squares to predict the results of the crosses • Compare and contrast the difference between an individual’s genotype and phenotype Why You Need To Know It… What You’ll Learn… • Heredity and genetics help explain why people are different

  3. Heredity – passing of traits from parent to offspring • What is Genetics? • Genes on chromosomes control organism’s form, function, and traits • Different forms of traits that make up a gene pair = alleles • Meiosis = pair of chromosomes separate, alleles also separate into different sex cells • Every sex cell has 1 allele for each trait • Study of how traits are inherited through interactions of alleles = science of genetics I. Inheriting Traits

  4. Gregor Mendel • Austrian Monk • 1865- studied pea plants to predict possible types of flowers and fruits resulting from cross breeding • 1st to trace on trait through several generations • 1st to use math = probability to explain heredity http://www.brainpop.com/science/cellularlifeandgenetics/heredity/ II. Mendel: Father of Genetics

  5. Mendel studied specific traits • Crossed 2 plants with different expressions of that trait • New plants all looked like one of the 2 parents • New plants called hybrids = received different genetic information (Diff. Alleles) for a trait from each plant 2. Organism that always produces the same trait generation to generation = purebred EX: Tall plants that always produce tall plants = purebred III. Genetics in a Garden

  6. Dominant and Recessive Factors • Cross pollination- pollinate one trait with opposite trait Ex: Purebred tall plants with purebred short plants 2. Dominant Allele = trait that covers up/dominants other form of that trait Ex: Tall gene covered short gene in plants 3. Recessive Allele = trait that is covered by the dominant trait http://www.brainpop.com/health/geneticsgrowthanddevelopment/genetics/ III. Genetics in a Garden

  7. Dominant and Recessive Factors

  8. B. Using Probability to Make Predictions • Probability- math that helps you predict the chance of something happening Ex: Coin toss – heads or tails – 50/50 chance 2. Mendel worked with a large number of plants – helped make predictions more accurate. Also increased the chances of seeing a repeatable pattern 3. Valid science conclusions need to be based on results III. Genetics in a Garden

  9. C. Punnett Squares • Letters represent dominant and recessive alleles • Uppercase letter = dominant allele • Lowercase letter = recessive letter • Letter – A code (genotype) = Genetic make-up • The way an organism looks or behaves is a result of genotype = phenotype Ex: Brown hair = phenotype of hair color = brown III. Genetics in a Garden

  10. D. Alleles Determine Traits • Most cells have 2 alleles for every trait • Alleles are located on chromosomes in nucleus of the cell • Organism with the same 2 alleles = homozygous trait EX: both tall alleles ( TT ) 4. Organism with that has 2 different traits EX: 1 tall and 1 short ( Tt ) 5. Mendel produced heterozygous hybrids for height = Tt III. Genetics in a Garden

  11. E. Making a Punnett Square • Letters representing 2 alleles from 1 parent are written along the top of the grid • Those of the 2nd parent are placed down the side of the grid (1 letter per section ) 3. Each square of the grid is filled with 1 allele donated by each parent 4. Letters represent genotypes of possible offspring that parents could produce T t T T III. Genetics in a Garden

  12. F. Principles of Heredity • Traits are controlled by alleles on chromosomes • An allele’s effect is dominant or recessive • When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate sex cells https://www.khanacademy.org/science/biology/heredity-and-genetics/v/punnett-square-fun III. Genetics in a Garden

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