B. Maize Crosses The inheritance of the extensive genetic variability in maize a
ID: 255132 • Letter: B
Question
B. Maize Crosses The inheritance of the extensive genetic variability in maize also obeys Mendelian principles, both seedling and aleurone (endosperm) characters lend themselves to classroom use. Figure 1.7 shows a flat of F2 seedlings segregating for a recessive mutant allele for albinism (absence of chlorophyll). The classical Mendelian ratio of 3:1 is expected. Similarly, Figures 1.8 and 1.9 show ears of F2 kermels of corn that are segregating in a ratio of 3colored: 1colorless aleurone typical of a monohybrid cross, or in a ratio of Icolored : 1colorless aleurone typical of a monohybrid testcross. Can you use the photos to confirm these expectations? Because maize has a relatively long life cycle (3 months or more to complete), you probably will not be able to conduct actual experimental matings with it. Your instructor might provide you with ears of genetic corn or flats of F2 seedlings and request that you determine the number of individual seeds or plants having the various phenotypes and then interpret the data in terms of Mendelian principles. For example, suppose you counted 40 green and 12 albino seedlings in an F2 population. How would you interpret these data? FIGURE 1.7 Flat of F2 corn seedlings segregating for a recessive al The classical Mendelian ratio of 3:1 is expected.Explanation / Answer
Answer:
Figure 1.7: flats of F2 seedlings segregating for a recessive mutant allele for albinism (absence of chlorophyll)
Based on the image, the count of the plants are:
Based on the given information:
For the F2 generation seedlings, there are two different phenotypes w.r.t color. Some seedlings are green in color and some seedlings are albino.
Number of green seedlings = 40
Number of albino seedlings = 12
Total number of seedlings = 40 + 12 = 52
Ratio of green:albino seedlings = 40:12 is approximately 3:1. This matches with the classical Mendelian monohybrid 3:1 ratio.
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