Need help with the pathways mostly. 1) (6 point question) A breeder had two diff

Question

Need help with the pathways mostly.

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 cros:s A B B. Green |A.bb Colorless Colorless Yellow A B- Colorless Green Yellow A B- ColorlessYellowGreen 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 B) (1 point) Can the biochemist rule out any of the pathways above based on the information he has from the breeder? Briefly explain your reasoning C) (2 points) What biochemical test could be done to narrow down the pathway to one of the three above

Explanation / Answer

1. A) Answer

A-B-= white

A-bb=white

aaB-=green

aabb=cannot be determined

A-B-=white

A-bb=white

aaB-=yellow

aabb=green

A-B-=white

A-bb=white

aaB-=green

aabb=yellow

B) answer: yes, based on the information from the breeder the biochemist can rule out first two proposed pathways.

it is showing the ratio of 12(white): 3 (green):1(yellow)

In the first case, the ratio is 12(white) : 3(green) but the fruits with yellow pigmentation cannot be determined due to lack of information about the genotype of C enzyme-coding gene which reflects the yellow colour,

in the second case, the yellow colour is masking the expression of green colour. it means green colour pigments produced only in homozygotic recessive condition(aabb). the maximum proportion of aabb genotype is 1/16, but breeder reporting green colour fruits are in the proportion of 3/16.

C) Answer: the biochemical test used to study the epistatic relations of genes is protein (here is an enzyme)activity assay. these are performed based on analysing the binding or catalysis of enzymes to its substrates. measuring either absorbance or fluorescence the enzyme activity could be detected.

Proposed pathway expected phenotypes in a dihybrid cross epistatic interaction 1 case 1( as per the table in the problem)

A-B-= white

A-bb=white

aaB-=green

aabb=cannot be determined

Enzyme A inhibiting the 1st step of the pathway in each case 2 case 2 ( as per the table in the problem)

A-B-=white

A-bb=white

aaB-=yellow

aabb=green

Yellow colour pigments are masking the green colour pigments when they together present in a fruit 3 case 3 ( as per the table in the problem)

A-B-=white

A-bb=white

aaB-=green

aabb=yellow

assume that green pigments would mask the yellow pigments if they occur together in the same fruit. a fruit with no pigments will be white.

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