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Cleft chin
Tongue Folders
Widow’s Peak
Hitch hiker vs. normal
thumb
Bent little fingers
Mid-digital hair
Six fingers/toes????
Interlaced Fingers
right over left or left over right???
PEDIGREE SYMBOLS
Autosomal
Recessive
Diseases
Diseases like:
Cystic Fibrosis
TaySachs
Phenylketonuria (PKU)
Using a Punnett square, cross two carrier parents of Cystic
Fibrosis—Write out your results for Phenotype & Genotype
N
N
n
NN
Nn
n
GR:
25% NN
50% Nn
25% nn
PR:
75% normal
25% Cystic
Fibrosis
Nn
nn
25% chance of child having CF—
50% chance of child being a
carrier of CF--
CYSTIC
FIBROSIS
Mutation in Chromosome 7 that causes a
defective protein in the plasma membrane.
Causes the formation of thick mucus in the
lungs and digestive tract.
This young girl is getting a treatment to
remove some of the mucus.
Most common in white Americans—one in 28
carries the recessive allele.
Tay Sachs—
Recessive allele causes the absence of an
enzyme that breaks down a lipid in the CNS.
More common in the Jewish population!
Infant becomes blind, deaf and has inability
to swallow!
Usually do not live past 3 years.
PKU--Phenylketonuria
What is PKU?
Individuals with PKU cannot process a part
of protein called phenylalanine, which is
present in most foods. Because of a genetic
abnormality, affected individuals lack or
have very low levels of an enzyme
(phenylalanine hydroxylase or PAH) that
converts phenylalanine to other substances
the body needs. Without treatment,
phenylalanine builds up in the bloodstream
and causes brain damage and mental
retardation.
How does PKU affect a child?
Children born with PKU appear normal for
the first few months. If untreated, by 3 to
6 months they begin to lose interest in their
surroundings. By the time they are 1 year
old, they appear obviously developmentally
delayed. Children with untreated PKU often
are irritable and have behavioral problems.
They may have a musty odor about them, and
they may have dry skin, rashes or seizures.
They usually are physically well developed
and tend to have blonder hair than their
siblings.
Who gets PKU?
Genes come in pairs. To inherit PKU, a child must receive two
abnormal PAH genes (that regulate the production of the
enzyme), one from each parent who has a mutation (change) in
one PAH gene. A parent who has one abnormal PAH gene is
called a "carrier." A carrier has one normal PAH gene and one
PAH gene that contains a mutation. A carrier's health is not
affected in any known way.
When both parents are carriers, there is:
A 1-in-4 (25 percent) chance that both will pass one abnormal
PAH gene on to a child, causing the child to be born with PKU.
A 2-in-4 (50-50) chance that the baby will inherit one abnormal
PAH gene from one parent and the normal gene from the other,
making it a carrier like its parents.
A 1-in-4 (25 percent) chance that both parents will pass on the
normal gene. The baby will neither have the disease nor be a
carrier.
These chances are the same for each pregnancy.
Are all babies tested for PKU?
All states and U.S. territories screen for PKU. Babies are
tested before they leave the hospital. The PKU test was the
nation's first newborn screening test. Developed with the help
of the March of Dimes, the test has been routinely
administered since the 1960s, sparing thousands of children
from mental retardation (2).
Can PKU symptoms be prevented?
Yes. Mental retardation can be prevented if the baby is treated
with a special diet that is low in phenylalanine. This diet should be
started as soon as possible after birth, ideally within the first
seven to 10 days of life (2).
At first, the baby is fed a special formula that contains protein
but no phenylalanine. Breast milk or infant formula is used
sparingly to supply only as much phenylalanine as the baby needs
and can tolerate. Later, certain vegetables, fruits, some grain
products (for example, certain cereals and noodles) and other lowphenylalanine foods are added to the diet. No regular milk, cheese,
eggs, meat, fish and other high protein foods are ever allowed.
Diet drinks and foods that contain the artificial sweetener
aspartame (which contains phenylalanine and is sold as Nutrasweet
or Equal) must be strictly avoided.
The diet for each person must be individualized, depending upon
how much phenylalanine can be tolerated. All affected persons
need regular blood tests to measure phenylalanine levels. Testing
for babies may be as frequent as once a week for the first year of
life, and then once or twice a month throughout childhood.
Individuals with PKU must remain on a restricted diet throughout
childhood and adolescence and generally for life (although some
relaxation of the diet may be possible as the person ages) (2).
Albinism—Caused by “recessive” alleles--
Albino Moose
Black Bear with Partial Albino Cub
Albino Alligator
Autosomal
Dominant
Condition
Disease like: Huntington’s Disease
Cross a homozygous recessive parent with a
heterozygous parent—Use a punnett square and
show results for Genotype and Phenotype.
H
h
h
Hh
Hh
h
hh
hh
GR: 50% Hh
50% hh
PR: 50% H. Disease
50% Normal
50% chance of H. Disease Carrier
50% chance of Huntington’s Disease
Definition—HUNTINGTON’S DISEASE
Huntington's disease is a progressive, degenerative disease
that causes certain nerve cells in your brain to waste away.
As a result, you may experience uncontrolled movements,
emotional disturbances and mental deterioration.
Huntington's disease is an inherited disease. Signs and
symptoms usually develop in middle age. Younger people
with Huntington's disease often have a more severe case,
and their symptoms may progress more quickly. Rarely,
children may develop this condition.
Also called Huntington's chorea, Huntington's disease was
documented in 1872 by American physician George
Huntington. The name "chorea" comes from the Greek word
for "dance" and refers to the incessant quick, jerky,
involuntary movements that are characteristic of this
condition.
Medications are available to help manage the signs and
symptoms of Huntington's disease, but treatments can't
prevent the physical and mental decline associated with
the condition.
The human achondroplasia phenotype, illustrated by a
family of five sisters and two brothers. The
phenotype is determined by a dominant allele. Also
called Dwarfism !
Codominance –Sickle Cell Anemia--
Work with your partner to answer the following: Chap 12
1. How is this disease codominant?
2. What is the effect of being heterozygous?
3. What population is affected most?
4. What is the mutation that causes SCA?
5. How common is this disease?
6. How do SCA patients avoid the effects of malaria?
Codominance—Roan color horse-Red and white hairs! Red Roan
Black and white hairs! Blue Roan
Anopheles Mosquito Injects…….
Plasmodium into blood…….
CAUSES MALARIA—FEVER, CHILLS, LOSS OF APPETITE, DEATH .
KILLS 1 MILLION TO 2.5 MILLION PEOPLE PER YEAR---AFRICA
Sickle cell trait is the genetic condition selected for in regions of
endemic malaria People with normal hemoglobin (2 normal genes=SS)
are susceptible to Plasmodium and thus can be infected with malaria
and die. People with sickle cell disease (2 sickle genes=ss) are
susceptible to death from sickle cell disease. People with one sickle
cell trait and one normal trait (heterozygous=Ss), have a much greater
chance of surviving malaria and are not affected by the adverse
effects of sickle cell disease. (SS=no sickle cells, Ss=some sickle cells,
ss=sickle cells)
Multiple Gene (Polygenic) Inheritance
abC
Gametes
ABC
ABc
AbC
Abc
aBC
aBc
abc
ABC
6
5
5
4
5
4
4
3
ABc
5
4
4
3
4
3
3
2
AbC
5
4
4
3
4
3
3
2
Abc
4
3
3
2
3
2
2
1
aBC
5
4
4
3
4
3
3
2
aBc
4
3
3
2
3
2
2
1
abC
4
3
3
2
3
2
2
1
abc
3
2
2
1
2
1
1
0
Table 1. Polygenic inheritance in people showing a cross between two mulatto parents (AaBbCc x
AaBbCc). The offspring contain seven different shades of skin color based on the number of capital
letters in each genotype.
Polygenic Inheritance: Human skin color is a good example of
polygenic (multiple gene) inheritance. Assume that three
"dominant" capital letter genes (A, B and C) control dark
pigmentation because more melanin is produced. The
"recessive"alleles of these three genes (a, b & c) control light
pigmentation because lower amounts of melanin are produced.
Multiple Alleles—When more than two
alleles are possible for the same trait!!!
Example:
Blood Types
What is blood made up of?
An adult human has about 4–6 liters of blood circulating in the body.
Among other things, blood transports oxygen to various parts of the
body.
Blood consists of several types of cells floating around in a fluid called
plasma.
The red blood cells contain hemoglobin, a protein that binds oxygen.
Red blood cells transport oxygen to, and remove carbon dioxide from,
the body tissues.
The white blood cells fight infection.
The platelets help the blood to clot, if you get a wound.
The plasma contains salts and various kinds of proteins.
Multiple Alleles—Blood types are determined by
more than 2 alleles. A is dominant to O. B is
dominant to O. A and B are co-dominant.
ii
OR
IAIA or IAi
IBIB or IBi
IAIB
Sample Blood Type Problems
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