ch 14 II - 1 Genetics In this human pedigree red and white...

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Unformatted text preview: 1/28/09 1 Genetics In this human pedigree, red and white indicate different phenotypes. White is dominant. The phenotype of the individual with a question mark was not recorded. What is the genotype of this person? A. WW B. ww C. Ww D. can’t tell E. this pedigree is impossible ? ? ww ww ww Ww Ww Ww ? In this human pedigree, red and white indicate different phenotypes. White is dominant. The phenotype of the individual with a question mark was not recorded. What is the genotype of this person? A. WW B. ww C. Ww * D. can’t tell E. this pedigree is impossible Complex crosses: If the genes sort independently, we can multiply individual probabilities PpYy (purple Fowered, yellow seeds) X PpYy What proportion of offspring will be white Fowered, with green seeds (ppyy)? from each parent, the chance of providing a pv gamete is 0.25 chance of gametes from both parents being py is 0.25 X 0.25 = 0.0625 = 1/16 py py PPYY PY PPYy PY Py pY py PpYY PpYy PPYy PpYY PpYy PPyy PpYy Ppyy PpYy ppYY ppYy Ppyy ppYy ppyy Py pY py Harder one PPYy X PpYy What proportion of offspring will be purple Fowered, with green seeds (P_yy)? ie., there is a .5 chance of getting the proper gamete from each parent and a .5 X .5 chance of getting P_yy = .25 Py must get the P allele; needs the y allele 1 X .5 = .5 will be Py already have the P allele from the other parent, so _y needed: 1 X .5 = .5 Py or py 1/28/09 2 PPYY PY PPYy PY Py pY py PpYY PpYy PPYy PPyy PpYy Ppyy Py P_yy offspring from PpYy X PPYy 1 in 4 Results of crosses are not always simple Incomplete dominance occurs when the phenotype is not all-or-nothing 1/500 people has a defective allele for the...
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ch 14 II - 1 Genetics In this human pedigree red and white...

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