1) (6 point question) A breeder had two different pure breeding lines of cantalo
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1) (6 point question) A breeder had two different pure breeding lines of cantaloupe; one with a white fruit the other with a yellow fruit. He crosses these two together and produces a hybrid that has white fruit. When he selfs the hybrid he finds that the progeny have either white, green or yellow fruit. The ratio of the progeny fruit color he observes is 12 white : 1 yellow : 3 green fruit. A) (3 points) A biochemist is interested in determining the pathway for pigmentation in cantaloupe. He hypothesizes potential biochemical pathways based on the 12:3:1 ratio seen by the breeder (there are others). Determine the expected phenotypes of the progeny based on the pathway shown. Then describe any epistatic interactions you see between the genes. (see a list of assumption below the table) Proposed pathway Expected phenotypes Epistatic interaction in a dihybrid cross A B- Green 1 ColorlessColorless Yellow Colorless Green Yellow A B Colorless YellowGreen .Assume that the green pigments would mask the presence of yellow pigments if they occur together in the same fruit. A fruit with no pigments will be white. Assume that the hypothesized C enzyme is wildtype (CC) in both pure bred lines Enzyme A acts by inhibiting the first step of the pathway in each case.Explanation / Answer
A)
A-B- =White
A-bb=white
aaB-=Green
aabb=Yellow
12(white): 3(green): 1(yellow)
A-B- = White
A-bb=White
aaB-=Yellow
aabb=Green
12(white): 3(Yellow); 1(Green)
A-B- =White
A-bb=White
aaB-=Green
aabb= Yellow
12(white): 3(Green): 1(Yellow)
B) Yes, Biochemist can rule out the 2nd proposed pathway in the table given. The information from the breeder state that there are white, yellow and green fruits in 12: 1: 3 ratio. But according to the 2nd pathway, there should be 12:3:1 that means yellow fruits should be in 3/16 th proportion, but the observation from the breeder it is 1/16 th proportion. so it is irrelevant.
C) Protein activity assay could be done to analyse the proteins involved in the pathways. Protein activity (enzyme activity) assay performed by evaluating the binding and catalysing activity of enzymes towards its substrates. By understanding which enzymes are active in each of the cases, they will come to know which pathway is active.
Proposed pathway Expected phenotypes in dihybrid cross Epistatic interaction 1A-B- =White
A-bb=white
aaB-=Green
aabb=Yellow
12(white): 3(green): 1(yellow)
Assumed that C-enzyme is wild type (CC) in both of purebred lines 2A-B- = White
A-bb=White
aaB-=Yellow
aabb=Green
12(white): 3(Yellow); 1(Green)
Yellow colour is masking the green colour when they together present in the same fruit 3A-B- =White
A-bb=White
aaB-=Green
aabb= Yellow
12(white): 3(Green): 1(Yellow)
Assume that green pigments would mask the yellow pigment If they are present in the same fruit. A fruit with no pigments would be in whiteRelated Questions
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