A plant which produces dark orange flowers is mated with a strain which produces

Question

A plant which produces dark orange flowers is mated with a strain which produces white flowers. The F1 plants produce light orange flowers. An F1 times F1 cross produces an F2 generation composed of 1/4 dark orange: 1/2 light orange: 1/4 white flowers. The mechanism of inheritance illustrated by this example is: a) complete dominance b) incomplete dominance c) epistasis-2 genes d) epistasis- 3 genes e) co-dominance If a heterozygous individual was crossed with a white flowered plant, _____ offspring would be produced. a) all dark orange b) all light orange c) 1/2 dark orange: 1/2 white d) 1/2 light orange: 1/2 white

Explanation / Answer

22. Answer (b)
Incomplete dominance is seen in cross-pollination experiments. In this monohybrid cross, the allele that produces the dark orange color (RR) is not completely expressed over the allele that produces the white color (rr). The resulting offspring are all light orange (Rr). The genotypes are: Dark orange (RR) X White (rr) = Light orange (Rr).
When the F1 (first filial) generation (consisting of all light range flower plants) is allowed to cross-pollinate, the resulting plants (F2 generation) consist of all three phenotypes [1/4 Dark orange (RR): 1/2 light orange (Rr): 1/4 White (rr)]. The phenotypic ratio is 1:2:1.

23. Answer (d)

Heterozygous individual i.e. light orange flower (Rr) X white flower (rr) = 1/2 Light orange flower (Rr) : 1/2 white color flower (rr).

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