What are the rules? - Biology Forum

last updated by

JackBean 14 years, 8 months ago

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3 replies

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- March 6, 2010 at 12:56 pm #12902
  mensamedlem
  Participant
  What are the rules to state the genotype of the individuals in a pedigree like this?
  Please explain it step by step of each individual so I understand the process.
  Squares = men
  Circles = women
  Yellow = sick
  Green = healthy
  A = sick
  a = healthy
  a) What is the mode of inheritance? Why?
  b) What are the genotypes of each individual?
  http://img21.imageshack.us/img21/9991/pedigree.gif
- March 8, 2010 at 6:44 am #98155
  JackBean
  Participant
  it’s apparently not dominant, because sick man has healthy children and vice versa.
  There are only men sick, but from two brothers, one is sick and the other healthy, so it’s probably not sex-linked.
  With these info, try to figure out the rest 😉
- March 9, 2010 at 10:36 am #98191
  mensamedlem
  Participant
  Then it must be autosomal recessive.
  Are the genotypes correct?
  A = sick
  a = healthy
  Generation 1:
  AA – Aa/aa – Aa – Aa
  Generation 2:
  Aa – Aa – Aa – Aa/aa – AA
  Generation 3:
  AA
- March 9, 2010 at 1:34 pm #98193
  JackBean
  Participant
  yes, that seems fine to me. Although I would use a for sick and A for healthy, but that’s your choice (just make it clear)
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