1. Inheritance Patterns

2. Gregor Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned experiments

4. Mendel’s Results

6. Mendel’s 3 Laws Law of Dominance Law of Segregation
Law of Independent Assortment

7. Law of Dominance There are two alleles for each gene
One is dominant over the other, which is recessive
Dominant means it is always expressed, recessive is only expressed if there are two copies of the allele

8. Mendel’s Laws: Law of Segregation
Sexual organism have two copies of a gene
One from mom and one from dad
The law of segregation states that the two alleles separate (segregate) during meiosis and end up in different gametes (sex cells)
Thus, an egg or a sperm gets only one of the two alleles that are present in the somatic cells of an organism

9. Mendel’s Laws: Law of Independent Assortment
The law of independent assortment states that each pair of alleles segregates independently of other pairs of alleles during gamete formation
Strictly speaking, this law applies only to genes on different, non- homologous chromosomes
Genes located near each other on the same chromosome tend to be inherited together

11. Non-Mendelian Inheritance

12. Incomplete dominance No dominant allele - blending
The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
Ex: a red and white flower makes a pink flower

13. P Generation Red CRCR White CWCW F1 Generation CR CW Gametes Pink CRCW2 2
Sperm
F2 Generation 1 CR 1 CW 2 2 1 CR 2
CRCR
CRCW
Eggs 1 CW 2
CRCW
CWCW

14. Codominance Two dominant alleles
Each allele affects the phenotype in separate, distinguishable ways
Ex: a red and white flower make a marbled, or speckled, flower

15. Multiple Alleles
Most genes exist in populations in more than two allelic forms
For example, the ABO Blood type system has 3 alleles:
The IA allele adds the A carbohydrate,
The IB allele adds the B carbohydrate;
The i allele adds neither

16. Blood Type Punnett square

17. Blood Typing lab!

18. Skin Color
How do we get skin color?

19. Polygenic Inheritance
AaBbCc
AaBbCc
aabbcc
Aabbcc
AaBbcc
AaBbCc
AABbCc
AABBCc
AABBCC
Polygenic inheritance results from an additive effect of two or more genes on a single phenotype
Skin color in humans is an example of polygenic inheritance
Eye color is another example: at least 8 genes code for eye color in humans
20/64
15/64
Fraction of progeny
6/64
1/64