HUMAN GENETICS

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HUMAN GENETICS
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KARYOTYPE
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Cleft chin
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Tongue Folders
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Widows Peak
Hitch hiker vs. normal thumb
Bent little fingers
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Mid-digital hair
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Six fingers/toes????
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Interlaced Fingers right over left or left
over right???
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PEDIGREE SYMBOLS
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Autosomal Recessive Diseases
Diseases like Cystic Fibrosis TaySachs Phen
ylketonuria (PKU)
Using a Punnett square, cross two carrier parents
of Cystic FibrosisWrite out your results for
Phenotype Genotype
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N
n
GR 25 NN 50 Nn 25 nn PR 75 normal 25
Cystic Fibrosis
NN
Nn
N
Nn
nn
n
25 chance of child having CF 50 chance of
child being a carrier of CF--
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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 Americansone in 28 carries the
recessive allele.
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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.
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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.
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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.
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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.
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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).
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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 low-phenylalanine 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).
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AlbinismCaused by recessive alleles--
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Albino Moose
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Black Bear with Partial Albino Cub
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Albino Alligator
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Autosomal Dominant Condition
Disease like Huntingtons Disease
Cross a homozygous recessive parent with a
heterozygous parentUse a punnett square and show
results for Genotype and Phenotype.
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H
h
GR 50 Hh 50 hh PR 50 H. Disease
50 Normal
hh
Hh
h
hh
h
Hh
50 chance of H. Disease Carrier 50 chance of
Huntingtons Disease
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DefinitionHUNTINGTONS 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.
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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 !
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Incomplete Dominance
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Incomplete Dominance OR CoDominance
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Codominance Sickle Cell Anemia--

• Work with your partner to answer the following
  Chap 12
• How is this disease codominant?
• What is the effect of being heterozygous?
• What population is affected most?
• What is the mutation that causes SCA?
• How common is this disease?
• How do SCA patients avoid the effects of malaria?

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CodominanceRoan color horse--
Red and white hairs! Red Roan
Black and white hairs! Blue Roan
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Anopheles Mosquito Injects.
Plasmodium into blood.
CAUSES MALARIAFEVER, 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 genesSS) are
susceptible to Plasmodium and thus can be
infected with malaria and die. People with sickle
cell disease (2 sickle genesss) are susceptible
to death from sickle cell disease. People with
one sickle cell trait and one normal trait
(heterozygousSs), have a much greater chance of
surviving malaria and are not affected by the
adverse effects of sickle cell disease. (SSno
sickle cells, Sssome sickle cells, sssickle
cells)  
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HUMAN SEX LINKAGE
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29
25
spots
45
56
spots
Spots ?
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6
8
spots
spots
5
2
8?
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Below are the correct answers to what a person with normal color vision would see - and what I see (and most people with Red-Green color blindness). When you see what we can't see, you may understand why it's so tough to find the right sox and why we like bright colors, which are often identifiable. Below are the correct answers to what a person with normal color vision would see - and what I see (and most people with Red-Green color blindness). When you see what we can't see, you may understand why it's so tough to find the right sox and why we like bright colors, which are often identifiable. Below are the correct answers to what a person with normal color vision would see - and what I see (and most people with Red-Green color blindness). When you see what we can't see, you may understand why it's so tough to find the right sox and why we like bright colors, which are often identifiable. Below are the correct answers to what a person with normal color vision would see - and what I see (and most people with Red-Green color blindness). When you see what we can't see, you may understand why it's so tough to find the right sox and why we like bright colors, which are often identifiable. Below are the correct answers to what a person with normal color vision would see - and what I see (and most people with Red-Green color blindness). When you see what we can't see, you may understand why it's so tough to find the right sox and why we like bright colors, which are often identifiable. Below are the correct answers to what a person with normal color vision would see - and what I see (and most people with Red-Green color blindness). When you see what we can't see, you may understand why it's so tough to find the right sox and why we like bright colors, which are often identifiable.
Normal Color Vision Normal Color Vision Normal Color Vision Red-Green Color Blind Red-Green Color Blind Red-Green Color Blind
  Left Right   Left Right
Top 25 29 Top 25 Spots
Middle 45 56 Middle Spots 56
Bottom 6 8 Bottom Spots Spots
Another interesting color blindness test is below Another interesting color blindness test is below Another interesting color blindness test is below Another interesting color blindness test is below Another interesting color blindness test is below Another interesting color blindness test is below
Last one in the middle The individual with
normal color vision will see a 5 revealed in the
dot pattern. An individual with Red/Green (the
most common) color blindness will see a 2
revealed in the dots
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Color Blind to some degree Normal vision
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• Red-Green color blindness is a genetically
  inherited condition in which people have trouble
  distinguishing between red and green.
• It is caused by a RECESSIVE gene carried on the X
  chromosome
• What is the probability of passing on the
  color-blind gene to a child if a mother is a
  carrier for color-blindness and the father does
  not have colorblindness?

Xn
XN

• How many girls will express the condition of
  color blindness?
• How many boys will express the condition of
  colorblindness?

XNXN
XNXn
XN
Normal vision
Normal vision
CARRIER
Y
XNY
XnY

• How many children will be carriers? What sex are
  they?

SEX-LINKED
Normal vision
Color blind
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Cross a colorblind male with a carrier
femaleShow the punnett square and your results!
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Genotypic Ratio 25 XNXn 25 XnXn 25 XNY 25
XnY Phenotypic Ratio 25 Carrier female
Normal female 25 CB female 25 Normal
male 25 CB male
Xn
XN
XNXn
XnXn
Xn
Colorblind female
Carrier female
Y
XNY
XnY
Color blind male
Normal vision male
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Diseases like Colorblindness Hemophilia
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SEX LINKED CONDITIONS---

• X linked conditions are seen more often in males
  than females because they have only 1 X
• Just like sickle cell anemia is found mostly in
  African American populations, Red-Green Color
  Blindness is found mostly in 1 population
• About 12-20 of Caucasian males have Red-Green
  Colorblindness
• This is about 1 in 20 Caucasian males
• And only 1 in 200 Caucasian females

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KARYOTYPE
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Karyotype
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The inheritance of the X-linked recessive
condition hemophilia in the royal families of
Europe.
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Hemophilia Problem Cross a carrier female of
hemophilia with a normal male! Show punnett
square and results!
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Genotypic Ratio 25 XNXN 25 XNXn 25 XNY 25
XnY Phenotypic Ratio 25 Normal female 25
Carrier female 25 Normal male 25 Hemophiliac
male
Xn
XN
XNXN
XNXn
XN
Carrier female
Normal female
Y
XNY
XnY
Hemophiliac Male
Normal male
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Multiple Gene (Polygenic) Inheritance
Gametes  ABC   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.


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Multiple AllelesWhen more than two alleles are
possible for the same trait!!! Example Blood
Types
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What is blood made up of?     An adult human has
about 46 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.  
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Multiple AllelesBlood types are determined by
more than 2 alleles. A is dominant to O. B is
dominant to O. A and B are co-dominant.
i i IAIA or IAi IBIB or IBi IAIB
OR
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Sample Blood Type Problems                      
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