5_Biol221 Lecture 5 01_27_11

This is graphically shown in the following diagram 52

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Unformatted text preview: type = aabb) and the resulting F1 plants are selfed, a modification of the dihybrid 9:3:3:1 ratio will be produced such that you get a 15:1 ratio. 48 Reverse geneAcs GeneAc Redundacy sep1 sep2 sep3 triple mutant shp1 shp2 double mutant 15:1 Ratio Genetic redundancy: both genes individually are sufficient for activity. 51 9:7 Ratio: Complementary Gene Action Flower color in sweet pea If two genes are involved in a specific pathway and functional products from both are required for expression, then one recessive allelic pair at either allelic pair would result in the mutant phenotype. This is graphically shown in the following diagram. 52 What does a 9:7 raAo really tell us? White w/w cross this to White w’/w’ Next generaAon we see complementaAon Purple W/w W’/w’ these guys are selfed What is the phenotype of the w/w ; w’/w’ ? Well…it’s white… We would expect 9 purple: 3 –grandparent w: 3 –grandparent w’ and 1 that has both traits from the grandparents. 9:7 RaAo: Complementary Gene AcAon 54 wt eyeless eye ­gone F1 wt cross eye ­gone eyeless wt sibling crosses 9 F2 eye ­gone eyeless doubles 3 eyeless 3 1 DEAD eye ­gone Embryonic lethal SyntheAc Lethality wt sibling crosses 9 F2 eye ­gone eyeless doubles 3 eyeless 3 1 DEAD eye ­gone Embryonic lethal SyntheAc Lethality 58 SyntheAc Lethality If mutaAons in A (eg a/a) or B (eg b/b) alone give a phenotype then you expect 9:3:3 raAo. However, it is ocen the case that a/a or b/b alone is wildtype and the raAo of phenotypes is 15:1 59 Recessive lethality and syntheAc lethality are not the same thing n or mm= wt TT or MM=dead Tt or Mm 60 Recessive lethality and syntheAc lethality are not the same thing n or mm= wt Tt or Mm TT or MM=dead 61 Recessive lethality and syntheAc lethality are not the same thing The embryonic lethality of Ay in the homozygous condiAon is most likely caused by the large deleAon and is unrelated to the ectopic expression of agou5 62 What if the Manx allele were discovered today in the age of molecular biology. MM = dead mm = wt Mm = tailless Full amount Half amount None 63 What if the Manx allele were discovered today in the age of molecular biology. mm = dead ? MM = wt ? Mm = tailless Full amount Half amount None 64 What if the Manx allele were discovered today in the age of molecular biology. mm = dead ? MM = wt ? Mm = tailless Full amount Half amount None An interesAng alternaAve interpretaAon of the same data is that wild type is parAally dominant over the severe recessive developmental defect, such that in the heterozygote, only the tail fails to develop. 66 What is the essenAal difference between recessive lethality and syntheAc lethality? Recessive (or Dominant) lethality refers to interacAons between alleles of the same gene SyntheAc Lethality refers to interacAons between alleles of different genes. 67...
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This note was uploaded on 01/20/2014 for the course BIOL 221 taught by Professor Gallagher,kimberly during the Spring '13 term at UPenn.

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