GENETICS
Basic Heredity
A study of gene inheritance from one
generation to the next.
History of Heredity
• Gregor Mendel is
father of modern
genetics
• Mendel used pea
plants to examine
heredity from one
generation to the
next
Mendel’s Laws
• 1) Law of Segregation
• There are two factors
controlling each trait
• These factors are “alleles”
• The alleles separate so that
gametes only get 1 of the two
alleles
• 2) Rule of Dominance
• One allele is always dominant
over the other
• 3) Law of Independent
Assortment
Genetics Rules
• Dominant alleles are written with CAPITAL letters
• Having 1 dominant alleles means the trait will be
expressed
• Recessive alleles are written with lowercase
• Must have 2 recessive alleles for the trait to be
expressed
Genotype vs. Phenotype
• Genotype: the alleles
(letters) an individual
has for a gene
• Phenotype: the way
the genotype is
expressed (looks)
Geno or Pheno?
• Tt
• HH
• Red hair
• BB
• Blue eyes
Genotypes
• Homozygous:
2 of the same
alleles for a
gene (TT, tt,
HH, etc)
• Heterozygous:
2 different
alleles for a
gene (Tt, Hh)
Hetero or Homo?
• BB
• Bb
• Hh
• tt
• dD