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If a mom and dad both have a
recessive trait in their DNA, what
is the chance that they BOTH pass
it on to one offspring?
• Lab #23
The modern study of genes in
all living things.
• Studying what genes do
• Studying how genes interact
• Studying how genes change
Each is a set of nucleic acids (nucleotide
bases) that code for a protein to be made.
Genes code for skin pigments, eye and
hair color, and many other things.
A segment of DNA
Actually made up of different
combinations of 4 letters- A, T, C, G
A pairs with T
C pairs with G
T
A
A
C
G
T
A
A
C
A
T
T
G
C
A
T
T
G
T
A
A
C
G
T
A
A
C
A
T
T
G
C
A
T
T
G
• Strands of letters tell the ribosome
what protein to make and how to make
it.
• *since you have two copies of each
gene (one from mom, one from dad,
they do not always agree.
• They interact in many different ways.
Dominance• Genes that will always show
if they are present. (CAPITAL)
Recessive• Both chromosomes must have
these genes for them to show.
(lower case)
Blue Eyes vs. Brown Eyes
• Brown eyes is a dominant color.
If EITHER of your chromosomes
hold the genes for brown eyes,
you will have brown eyes.
• Blue eyes are recessive, so you
can only have blue eyes if both of
your chromosomes hold the gene
for blue eyes.
Tay-Sachs Disease• Your cells have protein that
breaks down fat in your body.
• In Tay-Sachs, that protein is not
made, so fats build up in the brain
and cause brain function stop,
leading to death at a young age.
How do you inherit something from
your grandmother?
• Some traits disappear in one
generation, but reappear later.
• This is because a recessive trait
can be in your genes but not show
itself due to a dominant gene.
• Sexual vs. Asexual Reproduction
• Asexual- making an identical copy of
an individual (has the SAME DNA)
• Sexual- combines DNA of 2 parents,
offspring has half of each parent
Why do recessive traits keep getting
passed down if they are harmful?
• Lab #23