Download Human Genetics

Human Genetics
Ch 12
Chromosomal Mutations
Genetic Diseases….
Ultrasound
• Sonic picture of fetus
• Boy or girl?
Amniocentesis
Amniocentesis
• Remove amniotic fluid with baby’s cells
• Observe karyotype
• 1% risk to fetus
Amniocentesis
Nondisjunction
• Failure of homologous chromosomes to
separate properly during meiosis
• Karyotype will show extra or missing
chromosomes
Diseases from Nondisjunction
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Down’s syndrome extra 21
Trisomy 13 (Patau Syndrome)
Klinefelter’s syndrome 47 XXY
Turner Syndrome
45X
Edwards Syndrome Trisomy 18
Cri-du-Chat Syndrome missing part of
Chromosome #5
Link
Downs Syndrome Karyotype
Downs Syndrome
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1/700 live births
Extra chromosome #21
Mental retardation
Short
Heart defects
Same facial features
More frequent in mothers over 40
Downs Syndrome
Down’s Syndrome
Down’s Syndrome
Down’s Syndrome
Down’s syndrome
Trisomy 13
Trisomy 13
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Patau syndrome rare 1/20,000
Extra #13
Not alert
Deaf
Harelip
Cleft palate
Polydactyly
Live ~6 months
Trisomy 13 (Patau)
Trisomy 13
Trisomy 13
Kl inefelters Syndrome
Klinefelters
• 47 XXY
• 2/1000 male births
• Male but sterile
Turner’s Syndrome
Turners
• 45X_
• Female, usually sterile and sexually
immature
• Short, webbed neck
Turners 47
Turners 17
Edward’s Syndrome(Trisomy
18)
Edwards
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Extra #18
Smaller
Ears low and malformed
Webbed neck
Receding chin
Usually die of pneumonia or heart
failure
Cri-du-chat (missing part of
chromosome #5)
Cri-du-chat (missing part of
chromosome #5)
• Heart problems
• Mental retardation
• Abnormality in larynx - cries like a cat
Simple Recessive Heredity
1. Cystic Fibrosis (CF)
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Defective protein in plasma membrane
Mucus clogs lungs, liver, pancreas
1/20 white am. are carriers
1/2000 white americans born with CF
Physical therapy, special diet, drug
therapy, gene therapy raised life exp to
adulthood
2. Tay Sachs Disease
• Missing enzyme that breaks down a
lipid produced and stored in tissues of
the central nervous system
• Newborns appear normal for 5 months
• Blind, paralyzed, mentally retarded, die
before age 5
• 1/1600 Amish and Jews of Eastern
European descent
Baby with Tay Sachs
Video link
Children age 3-5 with Tay
Sachs
3. Phenylketonuria (PKU)
• Failure of brain to develop
• Absence of enzyme that converts
phenylalanine to tyrosine, so amino acid
builds up in the body
• Most common in people with ancestors
from Norway or Sweden
Testing
• Can detect in newborns, appear normal at
first, but milk is high in phenylalanine
Special diet
• Avoid foods with phenylalanine
• PKU warnings on diet foods
Mom with PKU
• Can have high phenylalanine in blood
and can damage the fetus even if the
fetus is normal
• Control diet
Simple Dominant Heredity
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Six fingers
Widow’s Peak
Free earlobes
Tongue rolling
Usually lethal genetic disorders result in
death before they can be passed on
Hapsburg Lip
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The above portrait is of Charles
II, who was King of Spain from
1665 to 1700, and who displays
this characteristic trait, a trait
that was passed down through
the Austro-Hungarian monarchy
through successive inbreeding.
ﾊ The Hapsburg lip deformity
affected poor Charles II so
badly that he could not chew his
food.ﾊ Years of inbreeding had
also taken its toll on his
intelligence (he was retarded)
and his powers of procreation
(he was impotent).
http://www.msu.edu/course/lbs/
333/fall/hapsburglip.html
1. Huntington’s Disease
• Causes the breakdown of the brain,
mental deterioration and loss of muscle
control
• Onset after age 30-50 (after had kids!)
• Can test to see if carrier and can pass
to kids and will develop the disease
Brain Deterioration
Huntington’s Disease
• 30,000 currently suffer in US
• Over 150,000 have 50% risk of
developing it
When Heredity Follows
Different Patterns
• 1. Incomplete Dominance
• Neither allele is dominant, but combine
to make a blended phenotype
• Ex: Red, white, pink carnations
• R = red pigment
• R’ = defective gene
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Incomplete Dominance cont.
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RR = Red
RR’ = Pink
R’R’ = White
What would the offspring look like if you
crossed Red and White?
• What would the offspring look like if you
crossed Pink and Pink?
2. Codominance
• Both alleles are expressed in heterozygous
offspring
• No dominant or recessive
• No blending
• Ex: Chickens
• B = Black feathers
W = white
2. Codominance
• What would a cross of a black chicken
and a white chicken look like?
• BB x WW
BW = checkered chickens!
Codominance - Sickle Cell
Anemia
• Affects African Americans and (white
Americans with Mediterranean Sea
ancestors)
• 1/12 African Americans are
heterozygous carriers
Codominance-Sickle Cell
Anemia
A
S
• SS = sickle cell anemia
• AS = sickle and normal cells and
protection from Malaria
3. Sex-linked Inheritance
• Genes on the sex chromosomes are
passed on differently in men and
women
• XX = female
XY = male
3. Sex-linked Inheritance
3. Sex-linked Inheritance
• Y doesn’t have the same alleles as X
• Ex: Color blindness, Duchenne’s
Muscular Dystrophy, Hemophilia
Colorblindness
Colorblindness
Colorblindness
3. Sex-linked Inheritance
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Color blindness:
XN = Normal Xc = colorblind recessive
No gene on Y
XNXc x XNY?
XNXc x XcY?
4. Polygenic Inheritance
• Trait controlled by many genes
• Phenotypes have a continuous range of
variability
• Ex: skin color, height
• Homozygous recessive = aabbcc
• Homozygous dominant = AABBCC
• Heterozygous
= AaBbCc
Eye Color
Height
5. Multiple Phenotypes
• Trait controlled by multiple alleles in a
population
• Each individual gets only 2 alleles
• Ex: Blood Types
• 3 Alleles: IA, IB, i
5. Multiple Phenotypes
• IA IA or IAi = A Blood
• IB IB or IBi = B Blood
• IA IB
=AB Blood
• ii
= O Blood
Donating Blood
• Immune system destroys foreign
proteins
• Type AB can accept all blood types
• Type A can accept ?
• Type B?
• Type O?
Mother and Child Reunion
Beth
Anti-A
Anti-B
Blood Type
Possible
Genotypes
Actual
Genotype
Sarah Baby 1 Baby 2 Baby 3
Questions
• 1. Which two babies are Beth’s twins?
• 2. Which baby is Sarah’s?
• 3. Now that you know the mother of
each baby, can you narrow down each
baby’s genotype?
• 4. What blood type is the twin’s father?
• 5. What are the possible blood types of
the father of Sarah’s baby? Explain!
6. Environment
• Temp, light, nutrition, chemicals, and
infections can all influence if a gene is
actually expressed.
• Internal Environment changes with age
or different hormones.
• Sex-Influenced trait: expressed
differently in males and females
Sex-influenced
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Ex: Male Pattern Baldness
Genotype
Male
Female
BB
Bald
Bald
Bb
Bald
Not bald
bb
not
not
Ex: Horn size in mountain sheep,
feather color in birds
Sex-Influenced trait
BB
or
Bb
Only
BB
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