1. Mendel and Genetics
I. Mendel’s Investigations

2. I. Mendel’s Investigations
A. Prior theory's
1. Blending Theory of Inheritance
a. offspring of two parents "blend" the traits of both
parents

3. I. Mendel’s Investigations
2. Particulate Theory of Inheritance
a. traits are inherited as "particles", offspring receive a
"particle" from each parent

4. I. Mendel’s Investigations
B. Some stuff about Mendel
1. parents were farmers
2. he became ordained as a priest
3. studied science and mathematics at the
University of Vienna

5. I. Mendel’s Investigations
C. Why study pea plants?
1. they are fast growing and easy to raise
2. They also have several visible characteristics that
may vary (purple vs white flowers, tall vs short
stems, round vs wrinkled seeds)

6. I. Mendel’s Investigations
D. Mendel’s laws
1. law of segregation
a. It states that there are two factors controlling a given
characteristic, one of which dominates the other
b. these factors separate and go to different gametes
when a parent reproduces.

7. I. Mendel’s Investigations
2. law of independent assortment
a. It states that factors controlling different
characteristics are inherited independently of each
other

8. I. Mendel’s Investigations
E. Genetics of inheritance
1. Characteristics of organisms are controlled by
genes on chromosomes at a locus

9. I. Mendel’s Investigations
2. In sexually reproducing organisms, each
individual has two copies of the same gene, one
copy comes from each parent

10. I. Mendel’s Investigations
3. The gene for a characteristic may have different
versions called alleles

11. I. Mendel’s Investigations
F. Genes and expression
1. Genotype
a. is the alleles an individual inherits
b. The two alleles may be the same (homozygote) or
different (heterozygote)

12. I. Mendel’s Investigations
2. Phenotype
a. The phenotype refers to the organism’s characteristics
or the expression of the genotype

13. Mendel and Genetics
II. Mendelian Inheritance

14. II. Mendelian Inheritance
A. Punnett square
1. is a chart that allows you to easily determine the
expected percents of different genotypes in the
offspring of two parents

15. II. Mendelian Inheritance
Ex) both parents are heterozygous for flower color
(Bb)

16. II. Mendelian Inheritance
B. Non-Mendelian Inheritance
1. Codominance
A. Occurs when both alleles are expressed equally in the
phenotype of the
heterozygote

17. II. Mendelian Inheritance
2. Incomplete dominance
a. Occurs when the dominant allele is not completely
dominant
b. Expression of the dominant allele is influenced by the
recessive allele, and an
intermediate
phenotype results

18. II. Mendelian Inheritance
3. Multiple Alleles
a. Many genes have multiple (more than two) alleles
b. An example is ABO blood type in humans, there are
three common alleles for the gene that controls this
A, B, O

19. II. Mendelian Inheritance
4. Polygenic Characteristics
a. Controlled by more than one gene, and each gene
may have two or more alleles
b. The genes may be on the same chromosome or on
nonhomologous chromosomes

20. II. Mendelian Inheritance
C. Effects of Environment on Phenotype
1. Genes play an important role in determining an
organism’s characteristics.
2. However, for many characteristics, the
individual’s phenotype is influenced by the
environment
a. If you have genes for great height but a poor diet you
will not reach your full potential