Transcript Additional Punnette Squares

Additional
Punnette Squares
Genetic Disorders:
The harmful effects produced by inherited
mutations.
Mutations:
 *are changes in genetic material
 *occurs when a gene is damaged, copied
incorrectly, or a faulty protein was made
Examples of Genetic Disorders

Sickle Cell Anemia – autosomal recessive
(red blood cells are sickle-shaped and
oxygen is not carried to cells)

Cystic Fibrosis – autosomal recessive
(production of thick sticky mucus – affects lung)

Huntington’s Disease – autosomal dominant
(neurodegenerative disorder – nerve cells start to degenerate)

Hemophilia – sex linked recessive
(rare bleeding disorder – blood does not clot properly)

Tay Sachs– autosomal recessive
(destroys nerve cells in the brain and spinal cord)

Phenylketonuria (PKU)– autosomal recessive
(causes intellectual and developmental disabilities because body cannot break down the
amino acid - phenylalanine)

Colorblindness– sex-linked recessive
(a deficiency of color vision; have difficulty in distinguishing certain colors)


Genetic Counseling – is a form of medical
guidance that informs people about genetic
problems that could affect them or their
offspring
Genetic Therapy – allows scientists to
correct certain recessive genetic disorders by
replacing defective genes with copies of
healthy ones
Sickle Cell Anemia

Sickle cell anemia is a recessive autosomal disease.
Michael and Kia are expecting their first child. Kia is
a carrier of sickle cell but Michael is not. They see a
genetic counselor who tells them that the probability
that their child will be a carrier of sickle cell is 50
___ %.
The probability that the child will have sickle cell is
_____
S
S
0 %.
S
SS
SS
s
Ss
Ss
Huntington’s is a dominant disorder.

Joe and his wife Betsy are both heterozygous
for Huntington’s. Their children have a ___
75 %
chance of having Huntington’s and a ___
25 %
chance of being normal. The probability that
their child will be a carrier of Huntington’s is
H
h
0 %.
_____
H
HH Hh
h
Hh
hh
Tay Sachs is autosomal recessive.

Janet and Lee are both heterozygous for Tay
Sachs disease. What are the odds that their first
child will be a carrier of Tay Sachs? ______%
50
What are the chances the child will have Tay
25 % What are the odds that their
Sachs? _____
child will be normal? ____%
75
T
t
T TT
t
Tt
Tt
tt
Colorblindness is x - linked recessive.

Jim’s father is color blind and his mother has
the gene for color-blindness but has normal
color vision. What are the odds that Jim is
color blind? ___
50 % How about his sister,
Sarah? What are her chances of being color
blind? ___
50 % What are her chances of being a
carrier of color-blindness?___
50 % Xc Y
Xc XcXc XcY
X XcX XY
Phenylketonuria (PKU)
is autosomal recessive.

Jane has PKU. Her husband, Darryl, neither
has the gene or is a carrier. What are the
chances that their children will have PKU?
____
Be a carrier
100
0 % Not have PKU? _____%
of PKU? ___
100%
P
p
Pp
p
Pp
P
Pp
Pp
Blood Types and Multiple Alleles

Blood type inheritance is somewhat complicated, with
three forms of the gene and 4 possible phenotypes.
Suppose that a man with heterozygous blood type B
marries a woman with heterozygous blood type A.
What are the possible blood types of their children?
___________________
AB, A, B, O
B
A
O
AB BO
O AO OO
Cystic Fibrosis
is an autosomal recessive disease.

Suppose that a man with a family history of CF marries
a woman with no history of the disease. The woman
has no genes for CF while the man is a carrier
(heterozygous) and does not have the disease. If these
people become parents, what are the chances that their
children will have CF? 0%
C
c
C CC Cc
C CC Cc