Inheritance of Traits: Pedigrees and Genetic Disorders

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Inheritance of Traits Pedigrees and Genetic
Disorders
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Pedigree definition

• Pedigree a family history that shows how a
  trait is inherited over several generations
• Pedigrees are usually used when parents want to
  know if they are carriers of a particular disorder

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Making a Pedigree
Filled in symbols indicate individual is affected
with a disorder

• Female
• Male
• Married Couple
• Siblings

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Example of a Pedigree
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
You
Brother
Do any disorders run in this family??
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Interpreting a Pedigree

• What can you tell from a pedigree?
• Whether a family has an autosomal or sex-linked
  disease or disorder
• Autosomal disorder appears in both sexes
  equally
• Sex-linked disorder allele is located only on
  the X or Y chromosome. Most sex-linked genes are
  on the X chromosome and are recessive
• So who would have an X-linked disorder more
  often, boys or girls?
• Whether a disorder is dominant or recessive

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Is this disorder 1) autosomal or sex linked, 2)
dominant or recessive?
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Sex Linked! (in this case allele is recessive and
located on the X chromosome)
You
Brother
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Is this disorder 1) autosomal or sex linked, 2)
dominant or recessive?
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Autosomal dominant!
You
Brother
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Is this disorder 1) autosomal or sex linked, 2)
dominant or recessive?
Grandparents
Grandparents
Parents
Aunts, Uncles
Aunts, Uncles
Autosomal recessive!
You
Brother
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Common Genetic Disorders

• Color blindness
• Sickle cell anemia
• Cystic Fibrosis
• Hemophilia
• Huntingtons Disease

For more info, go to http//www.ncbi.nlm.nih.gov
/pubmedhealth/
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Color Blindness

• Deficiency to percieve colors
• Problem with color-sensing pigments in certain
  nerve cells of the eye
• About 1 in 10 men have some form of color
  blindness.
• Sex-linked disorder

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Sickle Cell Anemia

• Disorder where abnormal hemoglobin (a protein
  inside red blood cells) is produced and warps red
  blood cells
• Sickle cells deliver less oxygen to bodys
  tissues and can get stuck in small blood vessels
• Recessive trait, tends to be seen in people of
  African or Mediterranean descent

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Cystic Fibrosis

• Recessive, autosomal disease
• Life threatening, causes thick mucus to build up
  in various areas of the body (lungs, digestive
  tract, etc).
• Tends to run in Caucasians, of Northern/Central
  European descent
• (1 in 29 Americans
• carry the allele)
• Average life span in US
• for people with CF is 37,
• death usually caused by
• lung complications

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Hemophilia

• Bleeding disorder, where it takes a long time for
  blood to clot (body lacks proteins involved in
  clotting)
• Sex-linked
• (carried on the X
• chromosome)
• Treatment
• involves
• injection with
• missing clotting
• protein

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Huntingtons Disease

• Autosomal, dominant
• Deterioration of brain tissue, usually begins
  between age 30 and 40.
• No cure, but have medications to cope with
  symptoms
• People usually die 15-20 years after onset of
• degeneration