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Pedigrees D-64 OGOS
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What is a pedigree? A pedigree is similar to a family tree, but is used to track a single trait throughout generations. This helps scientists and doctors understand how likely it is to pass this trait on to the next generation. Example: Tracking red hair in the Weasley family.
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Why do pedigrees matter?
Some inherited traits can be bad for the health of the offspring, such as Marfan Syndrome. Knowing how they occur can offer help in preventing them from happening or warn parents of the possibility. When it is known that someone could have a genetic disease, then doctors are able to test for and possibly treat it.
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How do they work? Is the affected trait dominant or recessive? How do you know? Dominant because it is present in all three generations on one side of Jim’s family, but not present at all in Kay’s family except for her son Tim.
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How do they work? Is Sue heterozygous or homozygous for the affected trait? How do you know? Heterozygous because if she were homozygous for the dominant trait all of her offspring would have it, but Sara does not.
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Most common misconception
How do scientists decide if a trait is dominant or recessive? Geneticists do not decide which trait is more dominant by seeing which is more common. They use pedigrees to look for patterns in offspring.
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Reading Follow along as we read pages D-64 to D-69.
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Marfan’s in Mrs. Anderson’s Family
Betty Bruce Jolene Mark Darla Sam Jorey Talked about on Page D-67
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PKU : Inability to break down amino acids
Can have: Delayed mental and social skills Head size significantly below normal Hyperactivity Jerking movements of the arms or legs Mental retardation Seizures Skin rashes Tremors Unusual positioning of hands Page D-67
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Polydactyly 1 6 5 2 4 3 Page D-69
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Key Things to Know Having more of a certain trait on a pedigree does not necessarily mean it is dominant. Circles represent females, squares represent males. Shaded individuals are the ones that show the trait being studied Generations of family members are connected by vertical lines, while people who married in are connected by horizontal lines.
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Is the shaded trait Dominant or Recessive?
Jan Homozygous Heterozygous Can’t tell
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Homozygous Heterozygous
Jan Homozygous Heterozygous Can’t tell
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Is the shaded trait Dominant or Recessive?
Marcus Homozygous Heterozygous Can’t tell
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Homozygous Heterozygous
Marcus Homozygous Heterozygous Can’t tell
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Is the shaded trait Dominant or Recessive?
Sophia Homozygous Heterozygous Can’t tell
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Homozygous Heterozygous
Two possibilities Sophia Homozygous Heterozygous Can’t tell What could scientists studying Sophia’s family do to determine whether the trait is dominant or recessive?
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Pedigrees Jan Marcus Sophia Homozygous Dominant Condition: Dominant
Homozygous Recessive Condition: Recessive Sophia Most Likely Heterozygous Homozygous recessive Condition: Most Likely Dominant Recessive
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Notebook… May 2nd Some people believe that traits of offspring are inherited as a blend of the two parents. Is this true? Why or why not How would you help someone who didn’t understand the way traits are actually inherited? How would this help them give up their original idea? What misconception have you overcome so far and what do you know now?
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