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Mendels Laws of Heredity Why we look the way we look...

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Presentation on theme: "Mendels Laws of Heredity Why we look the way we look..."— Presentation transcript:

1 Mendels Laws of Heredity Why we look the way we look...

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

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

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

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

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

7 Rule of Unit Factors b 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 b The trait that is observed in the offspring is the dominant trait (uppercase) b The trait that disappears in the offspring is the recessive trait (lowercase)

9 Law of Segregation b The two alleles for a trait must separate when gametes are formed b A parent randomly passes only one allele for each trait to each offspring

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

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

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

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

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

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

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


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