Gregor Mendel conducted early genetic research in the 1800s and is considered the father of genetics. Through experiments with pea plants, he discovered genes and the basic principles of heredity and inheritance. He found that traits are influenced by discrete factors, now known as genes, and that these genes are passed from parents to offspring. Genes exist in different forms called alleles, and offspring receive one allele for each trait from each parent. The combination of alleles determines the expressed phenotype. Mendel's work established the foundations of classical genetics.

1. Mendelian Genetics

2. I. History
• Gregor Mendel conducted the
earliest genetic research and is
known as the “Father or
Genetics” for his discoveries of
genes and inheritance
• He found organisms closely
resembled their parents with
slight variations and
characteristics are influenced
by heredity and the
environment

3. II. Genetics
• The branch of biology that studies HEREDITY,
which is the passing on of characteristics from
parent to offspring during sexual reproduction

4. III. Conclusions Made by Mendel
1. _TRAITS or physical characteristics are
influenced by GENES on chromosomes
o _GENE: Segment of DNA
-1 or more genes can determine a
hereditary trait

5. o There are two types of chromosomes, all
having different genes
a. _NON-SEX chromosomes
(autosomes)
b. _SEX chromosomes: X AND Y
Look at the
Karyotype…Which are the
autosomes? Which are the
sex chromosomes?
What is the gender?

6. 2. Genes have alternative forms called ALLELES
a. Offspring receives 1 allele from mom and dad
(One from each parent)
b. _TWO alleles determine how a trait is
expressed

7. Allele combinations on each homologous pair:
A. HOMOZYGOUS: HAS IDENTICAL alleles that
result in a dominant or recessive trait
Tall Pea Plant
TT
Short Pea
Plant
tt

8. Allele combinations on each homologous pair:
A. HETEROZYGOUS: HAS DIFFERENT alleles that
result in a dominant or recessive trait
• One allele is dominant and one
Tall Pea Plant
Tt is recessive
• DOMINANT: observed or
expressed trait (Capital
Letter)
• RECESSIVE: Weaker or
hidden trait (Lower Case
Letter)

9. Skip to Bottom of next page…
A. GENOTYPE: The allele combinations of an
individual (genetic makeup)
Ex. Trait: Flower Color
RR Rr rr
red red white

10. B. PHENOTYPE: The physical appearance of an
individual
Ex. Trait: Eye Color
You can “see” the phenotype, but you may not be
sure what alleles are exactly present.