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Introduction to Genetics
Abbott Gregor Mendel
• The “Father of Genetics”
1822-1884
• As you watch this video clip
write down 3 facts about
Gregor Mendel
https://www.youtube.com/watch?v
=YxKFdQo10rE
https://www.youtube.com/watch?v
=0vAAf4g5iF8
3 Main Principles
1) Segregation
• Alleles are separated
during reproduction; one
from each parent.
–Ex. BB (mom)
bb (dad)
»Child (Bb)
Segregation
• Alleles are
separated
during
reproduction;
one from each
parent.
2) Dominance
• In an heterozygous situation of
alleles (Aa for example), one
trait will be dominant (show up)
over the other.
• Ex. B= Brown eyes
b=
blue eyes
• BB= Brown eyes bb= blue eyes
• Bb= Brown eyes
3) Independent Assortment
• Which allele an organism
receives has no effect on
other traits which may be
displayed.
• Ex. Hair color has no effect
on Brain size.
So- What is Genetics?
• The study of the
path of
characteristics…ie
where they came
from, where they
are and where they
may go...
Why study genetics?
•Because
genetics
determine
WHO WE
ARE !!!
Alleles
• The different
forms of a gene
• A, B, Z
(anything!)
Homozygous -Purebred
•Two alleles of the same
dominance (either both
AA or both aa)
Heterozygous-Hybrid
•Two letters (alleles)
that are different =
hetero
•Ex. Aa or Zz or Bb.
Dominant /Recessive
• Dominant is represented
as an UPPER CASE Ex.
A
• Recessive is represented as
lower case. Ex. a
Phenotype
•The physical traits
that a person
actually shows!
Genotype
• The genes that a person
carries but does not show.
• Ex. A person may carry a
trait for blue eyes but
actually have Brown eyes!
Class survey
• Question- Are
dominant traits seen
more often than
recessive traits?
Free earlobes/Attached earlobes
Widows Peak/No widows peak
Cleft chin
Smile dimples
Two Factor Crosses
Incomplete Dominance
• A situation where one trait is not
completely dominant over the other. The
heterozygous trait is in between the
homozygous phenotypes.
Codominance
• A situation in
which both
alleles
contribute to the
phenotype of
the organism.
Multiple alleles
• Genes that have more than two alleles.
Polygenic Traits
• Genetic traits that are a combination of
several genes.