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Mendel’s Laws of Heredity

Mendel’s Laws of Heredity

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Mendel’s Laws of Heredity

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  1. Mendel’s Laws of Heredity Why we look the way we look...

  2. What is heredity? • The passing on of characteristics (traits) from parents to offspring • Genetics is the study of heredity

  3. Mendel used peas... • They reproduce sexually • They have two distinct, male and female, sex cells called gametes • Their traits are easy to isolate

  4. Mendel crossed them • Fertilization - the uniting of male and female gametes • Cross - combining gametes from parents with different traits

  5. Questions • What did Mendel cross? • What are traits? • What are gametes? • What is fertilization? • What is heredity? • What is genetics?

  6. What Did Mendel Find? • He discovered different laws and rules that explain factors affecting heredity.

  7. Rule of Unit Factors • Each organism has two alleles for each trait • Alleles - different forms of the same gene • Genes - located on chromosomes, they control how an organism develops

  8. Rule of Dominance • The trait that is observed in the offspring is the dominant trait (uppercase) • The trait that disappears in the offspring is the recessive trait (lowercase)

  9. Law of Segregation • The two alleles for a trait must separate when gametes are formed • A parent randomly passesonly oneallele for each trait to each offspring

  10. Law of Independent Assortment • The genes for different traits are inherited independently of each other.

  11. Questions... • How many alleles are there for each trait? • What is an allele? • How many alleles does a parent pass on to each offspring for each trait

  12. Questions... • What do we call the trait that is observed? • What case(upper or lower) is it written in? • What about the one that disappears? • What case is it written in?

  13. Phenotype & Genotype • Phenotype - the way an organism looks • red hair or brown hair • genotype - the gene combination of an organism • AA or Aa or aa

  14. Heterozygous & Homozygous • Heterozygous - if the two alleles for a trait are different (Aa) • Homozygous - if the two alleles for a trait are the same (AA or aa)

  15. Dihybrid vs Monohybrid • Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee) • Monohybrid Cross - crossing parents who differ in only one trait (AA with aa)

  16. Questions... • What is the phenotype? • What is the genotype? • What is homozygous? • What is heterozygous? • What is monohybrid crossing?