1. Mendel’s Laws of Heredity-Why we look the way we look...
EQ: What is the significance of Mendel’s
experiments to the study of genetics?

2. What is heredity?
The passing on of characteristics (traits) from parents to offspring
Genetics is the study of biological inheritance and variation in organisms.

3. Mendel used peas...

4. Mendel’s Pea Plants They reproduce sexually through self-pollination
Have both sex organs with two distinct, male and female, sex cells called gametes
Fertilization = sperm + egg

5. Mendel crossed them
Cross - combining gametes from parents with different traits
Line of plants (offspring) became purebred, genetically uniform

6. Genes and Alleles
Genes - located on chromosomes, they control how an organism develops and looks
Each organism has two alleles for each trait
Alleles - different forms of the same gene

7. What Did Mendel Find?
He discovered three laws and rules that explain factors affecting heredity.

8. 1. Rule of Dominance
The trait that is observed in the offspring is the dominant trait
expressed no matter what when present***
The trait that disappears in the offspring is the recessive trait
only expressed when two copies of the allele are present**

9. Rule of Dominance

10. 2. Law of Segregation
Organisms inherit two copies of each gene, one from each parent.
The two alleles for a trait must separate when gametes are formed during Meiosis
A parent randomly passes only one allele for each trait to each offspring **

11. 3. Law of Independent Assortment
The genes for different traits are inherited independently of each other.

12. 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

13. Heterozygous & Homozygous
Heterozygous - if the two alleles for a trait are different (Aa) (one dominant & one recessive )
Homozygous - if the two alleles for a trait are the same (AA or aa) (both dominant Or both recessive)