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.
