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Genetics
Why do we look the way we do?
Regents Biology
2004-2005
Inheritance of chromosomes
 Egg + sperm  zygote
meiosis
egg
zygote
sperm
Regents Biology
fertilization
mitosis &
development
2004-2005
Inheritance of genes
 On the chromosomes passed from
Mom & Dad to offspring are genes
may be same information
 may be different information

eye color
(blue or
brown?)
Regents Biology
eye color
(blue or
brown?)
2004-2005
Effect of genes
 _________________________________
_________________________
 _________________________
 _________________________

Regents Biology
2004-2005
Genes affect what you look like
X
Bb
BB
Regents Biology
Bb
Bb
Bb
Where did the blue eyes go??
bb
2004-2005
Genes affect what you look like…
X
Bb
BB
Regents Biology
Bb
Bb
Bb
Why did the blue eyes stay??
bb
2004-2005
Genes affect what you look like…
X
Bb
BB
Bb
Bb
Bb
bb
2004-2005
Where did the blue eyes come from??
Regents Biology
What did we show here?
 Traits come in “versions”
brown vs. blue eye color
 __________________

 Traits are inherited as separate units

brown & blue eye colors are separate &
do not blend
 brown x blue ≠ brown-blue eyes
 Some traits mask others

brown eye colors masked blue
Regents Biology
2004-2005
Paired chromosomes
Paired chromosomes have same kind of
information
 same types of genes
eye
color
(blue?)
hair
color
Regents Biology
eye
color
(brown?)
hair
color
2004-2005
Traits are inherited as separate units
 For each trait, an organism inherits
2 copies of a gene, 1 from each parent

a ____________ organism inherits
1 set of chromosomes from each parent
 ____________ = 2 sets of chromosomes
1 from Mom
__________________
1 from Dad
Regents Biology
2004-2005
B
Making gametes
 This all can be
BB
B
expressed using letters

flower color = P or p
BB = brown eyes
bb = blues eyes
Bb = brown flower
b
bb
b
B
Bb
Remember meiosis!
Regents Biology
b
2004-2005
B
How do we say it?
2 of the same
________________
BB = brown eyes
bb = blues eyes
BB
B
b
bb
b
2 different
________________
Bb = brown flower
Regents Biology
B
Bb
b
2004-2005
Punnett squares
_________________
female / eggs
male / sperm
Regents Biology
2004-2005
Genetics vs. appearance
 There can be a difference between
how an organism looks & its
genetics

appearance or trait = ___________
 brown eyes, blue eyes

genetic makeup = ___________
 BB, bb, Bb
2 organisms can have the same appearance
butBiology
have different genetics: BB vs Bb2004-2005
Regents
Genetics vs. appearance
How were these
brown eyes made?
eye
color
(brown)
eye
color
(brown)
eye
color
(brown)
eye
color
(blue)
vs.
B
BB
Regents Biology
B
Bb
B
b
2004-2005
Woof! Woof!
Any Questions?
Regents Biology
2005-2006