CHAPTER 12 HUMAN GENETICS

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CHAPTER 12HUMAN GENETICS
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Chromosomal Abnormalities

• 1 infant in 200 newborns has a
  chromosomal abnormality
• 28 of first trimester miscarriages have
  a chromosomal abnormality
• Abnormalities in larger chromosomes dont
  usually survive

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Color Blindness

• Cause
• Mutation in gene on X chromosome
• Symptoms
• More common in males (8 of males are
  colorblind)
• Cant distinguish certain colors
• Most common red/green

Can you see the numbers and shapes?
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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!

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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

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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

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Deletion
Piece of DNA code is lost
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Wolf-Hirschhorn syndrome

• Deletion on arm of chromosome 4
• Mental retardation
• Large low set ears
• Club feet

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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

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Prader-Willi Syndrome

• Deletion in chromosome 15
• Feeding problems poor weight gain in infancy,
  wont eat
• Ages 1-6 excessive, rapid weight gain

Victor at age 1 Victor at age 2
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Duchenne Muscular Dystrophy

• Symptoms
• Deletion in gene on X chromosome
• 1 in 3500 male births
• Appears before age 5
• Progressive muscle weakening
• Most in wheelchair by age 13
• Eventually lethal

Jerry Lewis telethon
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Non-disjunction

• A homologous pair sticks together and doesnt
  separate at MEIOSIS.
• One cell gets 2 copies of
• the chromosome the
• other cell gets none.
• Monosomy- 1 chromosome
• Trisomy- 3 chromosomes

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Downs 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

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Patau syndrome (trisomy 13)

• 1 in 7000 births (rare)
• Cleft lip palate
• Eye abnormalities
• (too small or missing)

low set ears
polydactyly
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Kleinfelter syndrome XXy

• 1 in 1000 births
• Male XXy
• Average to slight decrease in intelligence
• Small testes/cant have children
• Usually not discovered until puberty when dont
  mature like peers
• Has breast tissue poor beard growth

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Turners syndrome (X)

• 1 in 5000 births
• Female X
• Small size
• Slightly decreased intelligence
• Hearing loss common
• Undeveloped ovaries/cant have children

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Xyy syndrome

• Xyy males
• Taller, more aggressive
• Some early studies showed greater incidence of
  Xyy males in prison populations than in the
  normal population

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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.

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Sickle Cell Anemia

• Substitution on chromosome 11
• A is changed to T

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Insertion (addition)
Extra Piece of DNA is added to code
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Huntingtons

• 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?
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How can we detect disorders?
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Karyotype
What is wrong with this karyotype?

• Can tell missing/extra chromosomes
• Gender
• Some deletions/additions

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Amniocentesis

• Insert needle into sac and withdraw
• fluid containing babys cells
• Done at 14-16 weeks
• Can detect
• Cystic Fibrosis
• Huntingtons
• missing/extra chromosomes

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The End.