GENETICS
Have you ever wondered…
• How no two people have the same fingerprints?
• How two brown cows can have a white calf?
• Why you have green eyes when both parents
have blue?
• Why you can roll your tongue and your friend
can’t?
• These questions can all be answered through
genetics, the study of heredity.
Genetics
• A general understanding of how heredity works has
existed for a very long time.
• Over 5000 years ago, Native Americans used their
understanding to develop corn through a process of
selective breeding. ( we’ll get back to this)
Father of Genetics
WHYYY?!
• The foundation for genetics, as we know it
today, was laid by a monk / priest named
Gregor Mendel.
• 1851 – Mendel began his studies on
genetics through experiments with pea
plants.
• He observed that the pea plants had traits
that were often similar to their parents.
• However, sometimes the pea plants had
different traits than their parents.
Mendel’s Experiment
• Why did the
shortness trait
disappear?
• Why did it
reappear in the
next
generation?
The Discovery of Genes and Alleles
• Mendel reasoned that individual “factors” must control the
inheritance of traits.
• The “factors” exist in pairs: the female contributes one
and the male contributes one.
• We now refer to the “factors” that control traits as genes.
• The different forms of a gene are called alleles.
Dominant vs. Recessive
• Mendel discovered that one of the alleles can sometimes
mask, or hide, the other allele just like tallness masked
shortness in the peas.
• A dominant allele is one whose trait always shows up in
the organism when the allele is present.
• Represented with a capital letter
• Ex: (T) tall
• A recessive allele is masked, or covered up, whenever
the dominant allele is present.
• Represented with a lowercase letter
• ex: (t) short
Dominant vs. Recessive
T
t
TT
Tt
TT
Tt
T
t
T
TT
Tt
t
Tt
tt
T
T