1. MENDEL AND THE GENE IDEA

2. Gregor Mendel Austrian monk
Brought experimental and quantitative approach to genetics
Bred pea plants to study inhertance
Why peas?
Control mating (self- vs. cross-pollination)
Many varieties available
Short generation time

3. P (parental) generation = true breeding plants
F1 (first filial) generation = offspring
F2 (second filial) generation = F1 offspring

4. 7 characters in pea plants (observed 3:1 ratios)
Dominant vs. Recessive (expressed) or (hidden)

5. Mendel’s Model
Tried to explain the 3:1 inheritance pattern he saw among the F2 offspring using 4 basic concepts

6. First- alternative versions of genes accounts for variations in inherited traits Alleles: alternate versions of a gene

7. Second- an organism inherits two alleles, one from each parent
Second- an organism inherits two alleles, one from each parent. A genetic locus is represented twice

8. dominant (P), recessive (p)
THIRD-IF two alleles at a locus differ then the dominant allele determines the organisms appearance
dominant (P), recessive (p)
homozygous = 2 same alleles (PP or pp)l; fully epxressed
heterozygous = 2 different alleles (Pp); no noticeable effect; gene make a non-functional protein

9. Fourth-Law of Segregation
The two alleles for a heritable character separate (segregate) during gamete formation and end up in different games

10. MENDEL’S PRINCIPLES
Alternate version of genes (alleles) cause variations in inherited characteristics among offspring.
For each character, every organism inherits one allele from each parent.
If 2 alleles are different, the dominant allele will be fully expressed; the recessive allele will have no noticeable effect on offspring’s appearance.
Law of Segregation: the 2 alleles for each character separate during gamete formation.

11. Law of Independent Assortment:
Each pair of alleles segregates (separates) independently during gamete formation
Eg. color is separate from shape

12. Testcross: determine if dominant trait is homozygous or heterozygous by crossing with recessive (pp)

13. Phenotype: expressed physical traits
Genotype: genetic make-up

14. Punnett Square Device for predicting offspring from a cross
Example: Bb x Bb (B=purple, b=white)
Genotypic Ratio: 1 BB, 2 Bb, 1 bb
Phenotypic Ratio: 75% or 3/4 purple and 25 % or ¼ white

15. Monohybrid cross: study 1 character
eg. flower color
Dihybrid cross: study 2 characters
eg. flower color & seed shape

16. Dihybrid Cross (video)
Example: AaBb x AaBb
F: Take the FIRST allele of each gene (left eyebrow) to make one possible gamete. O: Take the OUTER alleles (big smile) to make one possible gamete. I: Take the INNER alleles (nose curve) to make one possible gamete. L: Take the LAST allele of each gene (right eyebrow) to make one possible gamete.

17. Segregation of alleles and fertilization as chance events
Probability Rules:
AND= multiply
½ x ½ = ¼
OR=add
¼ + ¼= 2/4 =1/2