Transcript HUMAN GENETICS Chapter 12 - Goshen Community Schools

CHAPTER 12
HUMAN GENETICS
Chromosomal Abnormalities
• 1 infant in 200 newborns has a
chromosomal abnormality
• 28% of first trimester miscarriages have
a chromosomal abnormality
• Abnormalities in larger
chromosomes don’t usually survive
Color Blindness
Cause:
Mutation in gene on X
chromosome
Symptoms:
• More common in males
(8% of males are colorblind)
• Can’t distinguish certain
colors
• Most common = red/green
Can you see
the numbers
and shapes?
Hemophilia
Cause:
change in gene on X chromosome that codes
for blood clotting protein
Symptoms:
• More common in males
• Internal and external bleeding
•Can result in death
•Transfusions & hospitalization
are required frequently to
stop bleeding!
Cystic Fibrosis
• Mutation in gene on chromosome 7
• Symptoms:
– More common in Caucasians
– Make extra thick mucous in lungs and
pancreas which leads to respiratory and
digestive complications
– Salty skin is clue
Achondroplasia
(Dwarfism)
Cause: (Autosomal DOMINANT- found on chromosome 4)
Most new mutations in egg or sperm cell, but can be inherited
from parent with gene
•1 in 20,000 births
•200,000 “little people” worldwide
•Normal size torso;
short arms and legs
Deletion
Piece of DNA code is lost
Wolf-Hirschhorn syndrome
• Deletion on arm of
chromosome 4
• Mental
retardation
• Large low set ears
• Club feet
Cri-du-chat “cry of the cat”
• Deletion on arm of
chromosome 5
• 1 in 50,000 births
• More common in girls
• Mewing cry in infancy
• Mental retardation
Prader-Willi Syndrome
• Deletion in chromosome 15
• Feeding problems: poor weight gain in
infancy, won’t eat
• Ages 1-6 excessive, rapid weight gain
Victor at age 1
Victor at age 2
Duchenne Muscular Dystrophy
Symptoms:
• Deletion in gene on X chromosome
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1 in 3500 male births
Appears before age 5
Progressive muscle weakening
Most in wheelchair by age 13
Eventually lethal
Jerry Lewis telethon
Non-disjunction
A homologous pair sticks together and
doesn’t separate at MEIOSIS.
One cell gets 2 copies of
the chromosome the
other cell gets none.
Monosomy- 1 chromosome
Trisomy- 3 chromosomes
Down’s syndrome (trisomy 21)
•Most common
chromosomal abnormality
•1 in 660 births
•Similar facial features
•Slanted eyes
•Protruding tongue
•Mental retardation
•Risk increases with age of
mom
Patau syndrome (trisomy 13)
•1 in 7000 births (rare)
•Cleft lip & palate
•Eye abnormalities
(too small or missing)
low set ears
polydactyly
Kleinfelter syndrome XXy
•1 in 1000 births
•Male = XXy
•Average to slight decrease in intelligence
•Small testes/can’t have children
•Usually not discovered until puberty when don’t mature like peers
•Has breast tissue & poor beard growth
Turner’s syndrome (X)
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1 in 5000 births
Female = X
Small size
Slightly decreased
intelligence
• Hearing loss common
• Undeveloped
ovaries/can’t have
children
Xyy syndrome
• Xyy males
• Taller, more aggressive
• Some early studies showed
greater incidence of Xyy
males in prison populations
than in the normal
population
Substitutions
Can YOU find the difference?
the fat cat ran and ran
the fat rat ran and ran
Sickle Cell Anemia is caused by this.
Sickle Cell Anemia
•Substitution on
chromosome #11
A is changed to T
Insertion (addition)
Extra Piece of DNA is added to code
Huntington’s
• Insertion at end of gene on
chromosome 4
• Degenerative brain disorder
• Symptoms appear at
age 30-40
(Usually after having children)
• Lose ability to walk, think,
talk, reason
• 50/50 chance of passing it to
child
Now there is a test
to tell if you have
the gene before
symptoms appear.
Would you want to know?
How can we detect disorders?
Karyotype
What is
wrong with
this
karyotype?
•Can tell missing/extra chromosomes
•Gender
•Some deletions/additions
Amniocentesis
•Insert needle into sac and withdraw
fluid containing baby’s cells
•Done at 14-16 weeks
•Can detect:
•Cystic Fibrosis
•Huntington’s
•missing/extra chromosomes
The End.