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Idiots guide to analysing pedigree charts


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useful information for those trying to work out what is happening in a pedigree chart

Idiots guide to analysing pedigree charts

  1. 1. The idiots guide to pedigree chartsKey  to  pedigree   Key  to  alleles  charts     D  =  dominant  allele   Not   Affected   d  =  recessive  allele   affected   XD  =  dominant  allele  on  the  X  chromosome   Xd  =  recessive  allele  on  the  X  chromosome  Female   Y  =  Allele  not  carried  on  the  Y  chromosome   Male   Chris  Paine          h?ps://  
  2. 2. A   B  Disease  caused  by  a  dominant  (D)  allele   A   gametes   D   d   D   DD   Dd   look  for  two  affected  parents   B   producing  a  normal   individual   d   Dd   dd   Chris  Paine          h?ps://  
  3. 3. A   B  Disease  caused  by  a  recessive  (d)  allele   A   gametes   D   d   look  for  two   unaffected  parents   D   DD   Dd   producing  an   affected  individual   B   d   Dd   dd   Chris  Paine          h?ps://  
  4. 4. Disease  caused  by  a  dominant  (D)  allele   in  dominant  diseases     usually  more  than   25%,  by  probability   50%  of  individuals  in   a  pedigree  chart  will   be  affected   Chris  Paine          h?ps://  
  5. 5. Disease  caused  by  a  recessive  (d)  allele   In  recessive  diseases   affected  individuals   oQen  occur  every   other  generaRon     Chris  Paine          h?ps://  
  6. 6. Disease  is  sex-­‐linked  (carried   on  the  X  chromosome)   most  if  not  all   affected  individuals   will  be  male   Chris  Paine          h?ps://  
  7. 7. Disease  is  sex-­‐ linked  (carried   on  the  X   A   B   chromosome)   A   gametes   Y   Xd   females  maybe   XD   Y  XD   XDXd   affected,  but  only  if  B   the  male  parent  is   affected   Xd   Y  Xd   XdXd   Chris  Paine          h?ps://