1. The Story of the Monk and the Pea…
Mendel’s Laws of
Heredity
The Story of the Monk and the Pea…

2. Once upon a time in a far away place (a. k. a
Once upon a time in a far away place (a.k.a.Austria) lived a dude by the name of Gregor Johann Mendel…

3. The son of a peasant farmer…

4. Studied to become a teacher..

5. Became obsessed with peas….

6. Like all the other greats he knew his time would come…

7. The science behind the legend…
The peas reproduce sexually
They have two distinct, male and female, sex cells called gametes
Their traits are easy to isolate

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

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

10. Rule of Unit Factors Each organism has two alleles for each trait
Trait – a specific characteristic (seed color, plant height)
Alleles - different forms of the same gene
Genes - located on chromosomes, they control how an organism develops

11. Alleles

12. 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)

13. Rule of Dominance…

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

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

16. 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

17. 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)

18. Dihybrid vs. Monohybrid
Monohybrid Cross - crossing parents who differ in only one trait (AA with aa)
Zork Genetics
Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee)
More Zork Genetics

19. What does Meiosis have to do with this?
Genes
Chromosomes
REMEMBER
Males have XY chromosomes
Females have XX chromosomes

20. MEIOSIS  HAPLOID CELLS
REVIEW
MEIOSIS  HAPLOID CELLS
REDUCTION IN THE NUMBER OF CHROMOSOMES PER CELL
46  23