Variegated Cell division Green White Egg type 1 Egg type 2 Egg type 3 Egg cell of female (n) Pollen cell of male Zygote constitution (2 n ) White Any Green Variegated Any Any Green White Nucleus Chloroplast ± ± ± ± ± Figure 2-31 A model explaining the results of the Mirabilis jalapa crosses in regard to autonomous chloroplast inheritance. The large, dark spheres are nuclei. The smaller bodies are chloroplasts, either green or white. Each egg cell is assumed to contain many chloroplasts, and each pollen cell is assumed to contain no chloroplasts. The ﬁrst two crosses exhibit strict maternal inheritance. If, however, the maternal branch is variegated, three types of zygotes can result, depending on whether the egg cell contains only white, only green, or both green and white chloroplasts. In the last case, the resulting zygote can produce both green and white tissue, so a variegated plant results. 57
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.