1. Genetics

2. Introduction to Genetics
Gregor Mendel- 19th Century (1800’s)
Austrian monk
1st important studies of heredity
Heredity–
Passing on of characteristics from parents to offspring

3. Chose to study the pea plant (Piscium sativum)
Reproduce sexually
Both male and female gametes are on the same flower

4. Mendel studied only one trait at a time
Traits are passed from parent to offspring

5. Pea plant’s structure Allowed Mendel to fertilize plants
Reproduce and develop quickly
They appeared to have traits that were either one or the other (green OR yellow, smooth OR wrinkled)

6. Gamete = male or female sex cells

7. Transfer of male gamete (pollen) to female sex structure (pistil) = pollination
Fertilization = Joining of male and female sex cells
Forms a zygote- fertilized egg

8. Rule of Unit Factors Found on chromosomes in egg and sperm
Mendel concluded that 2 alleles control each trait
One from ma, one from pa
Those 2 alleles code for genes
Alternate forms of a gene are called alleles
Found on chromosomes in egg and sperm

9. Rule of Dominance There are generally 2 alleles for a given trait
Dominant = Expressed when at least one dominant allele present
Recessive = Must have two recessive alleles to be expressed

10. Here is an example
The tall allele (T) is dominant over the short, recessive allele (t) in pea plants
Therefore; TT = tall; Tt = tall; tt = short
Letters for the alleles are decided by the dominant trait.

11. Genotype The genetic makeup of an individual The letters
Includes both genes in a homologous pair of chromosomes
Pure bred YY, TT, PP, GG, yy, tt, pp, gg
Hybrid Yy, Tt, Pp, Gg

12. Phenotype The outward expression of a trait
Ex: Brown fur, attached ears, cleft chin, widows peak

13. Homozygous The two alleles in a gene pair are identical
TT, tt, PP, pp, GG, gg
Also called Purebred
A purebred Friesian

14. Heterozygous The two alleles for a particular trait are different.
Tt, Pp, Gg, Hh, Nn, Mm
Also called hybrid
“Hercules” the Liger

15. Law of segregation
Alleles separate when gametes are made during Meiosis (a process we will go into later)
Half the gametes will contain one gene/allele the other half will contain the other gene/allele

16. Genetics and Punnett Squares
Punnett square show possible offspring of parents with a specific trait
Possible gametes of parents are letters on outside H h HH Hh H Hh h hh

17. Recessive Traits Cystic fibrosis- Type of lung disease
Tay Sachs- mental/physical
break down
Albinism

18. Dominant Traits Huntington disease- nerve cells break down over time
Polydactyly