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Gene for
nose size
Nucleus
Cell
Gene for hair
color
23 pairs of
chromosomes
Gene for
freckles
Cell preparing for cell division.
Chromosomes line up along an invisible center
line in the nucleus and get torn apart.
DNA “unzips” and copies itself so that the
duplicate cell receives the same type and number
of chromosomes
Mitosis in action!
The gene for hair
color on this
chromosome is
turned “on” and this
cell will make the
protein to give the
person brown hair
In each cell
made,
one gene is
selected to
be turned
“on” to
have that
cell make a
certain
protein
that will
make a
certain
trait.
The gene on this
sex chromosome
for making a
protein that will
make a gamete is
turned “on”
X or Y
chromosome
In each cell
made,
one gene is
selected to
be turned
“on” to
have that
cell make a
certain
protein
that will
make a
certain
trait.
23 individual
chromosomes
(not 23 pairs)
Gamete Cell:
sperm or egg
Egg
Sperm
Egg
Sperm
Egg
Sperm
Egg
Sperm
Nucleii and chromosomes of each cell
come closer together
Egg
Sperm
“Like” chromosomes of each cell meet up
near an imaginary center line between the
two cells
Egg
Sperm
Chromosomes from each cell begin
exchanging DNA information:
“swapping genes”
Egg
Sperm
Fertilized egg moves away from the sperm
cell. The sperm cell dies, and the fertilized egg
develops into an embryo.
Offspring
This boy has
inherited all of
his traits from
his parents.
They are a
combination of
some of mom’s
traits, and also
some of dad’s
traits.
Each of his
traits can be
studied to know
why they look
the way they
do. This study
is known as…
GENETICS!
Let’s focus on
the trait of his
hair color.
Mom
Dad
Mom’s phenotype:
Mom goes to
the salon and
has her hair
colored. Her
natural hair
color is
brown.
Dad’s phenotype:
Dad highlights
is hair as well,
but his
natural hair
color is also
brown.
Mom’s Genotype:
Bb
Dad’s Genotype:
Bb
I wonder
how I got
brown hair
???
I can do a
Punnett
Square!!!!
There was a 75%
chance of the
offspring having
brown hair. The
“big B” showed
up in 3 out of the
4 squares when
we crossed
mom’s alleles
with dad’s alleles
using a Punnett
Square.
There is a
25% chance
of mom and
dad still
having a
child with
blonde hair.
“bb” tells me
so.
So that is
why my hair
is brown!
I can keep
up on
genetics,
and use a
Punnett
square on
each of my
traits!
I think
heredity
is cool!
Mutation
Mayhem!