2. You are studying the genetics that control flower color in poppies. After a l

Question

2. You are studying the genetics that control flower color in poppies. After a lot of hard work you think you have figured out the pathway (see drawing below). You think that gene A converts a precursor into a yellow pigment. This yellow pigment can be converted into an orange pigment by either gene B or C. Gene D acts as a dominant inhibitor of gene A such that a single copy of D blocks A. Gene D Gene B Gene A Intermediate Precursor (White) Prwbite)(Yellow) Final product (Orange) You cross two plants that are both AaBbCcDd to each other. Predict the phenotypic segregation ratios that you expect to see if this pathway is correct. row the obtain seeds from this cross and plant 600 plants. You observe 454 plants with You g white flowers, 133 plants with orange flowers and 13 observations support your hypothesis? plants with yellow flowers. Do these

Explanation / Answer

We are crossing two plants with the genotype- AaBbCcDd

The total number of combinations it can make is 44 =256
Now. a colored flower will only form when dd is present, the chances of that happening is- 1/2 * 1/2 =1/4
= 256/4
=64

Number of white flower= 256-64 = 192

Now the chances of having bb and cc both present (which will result in a yellow flower is) = 1/2 * 1/2 * 1/2 * 1/2 = 1/16
i.e 64/16 = 4

Number of orange flower = 64-4 = 60

White: Orange: Yellow = 192:60:4 = 48: 15: 1

The observed ratio is= 454: 133: 13 = 34: 10: 1 (which supports the hypothesis)

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