1. GENETICS REVIEW
• We get our genes from our parents
– Half from our mom & half from our dad
• Genes are represented by 2 letters
– This is the genotype
– Each letter can be capital (dominant) or lower
case (recessive)
– Genotypes can be homozygous or heterozygous
– Homozygous – 2 letters are the same
• Example: HH or hh
– Heterozygous – the 2 letters are different
• Example - Hh

2. GENETICS REVIEW, continued
• Phenotype – tells how the genes look
– Example, eye color – blue is recessive (b)
– Brown is dominant (B)
• BB is a homozygous genotype --- the
phenotype is BROWN
• Bb is a heterozygous genotype --- the
phenotype is BROWN
• bb is a homozygous genotype --- the
phenotype is BLUE

3. GENETICS REVIEW, CONTINUED
• We can predict the possible traits show with
Punnett Squares
• Break the genotypes up, put each letter over
the top or down the side
• Then you drag each letter down into each box
What is the B B
chance of a man Zero percent
b
with blue eyes chance. In order
Bb Bb for blue eyes to
and a female
with brown eyes appear you need 2
(homozygote) Bb Bb recessive alleles.
b
having a blue The female on has
eyed child? 2 dominant alleles.