Stem height of tobacco plant with genotype aaBbCc is 30 cm and the minimum is 20 cm. Find out the height of plant with genotype aabbCc if the character is controlled by three pair of polygenes.
(1) 25 cm (2) 35 cm
(3) 20 cm (4) 30 cm

Dear student,
Please find below the solution to the asked query

The correct option is (1).
Stem height in tobacco is controlled not by a single pair of gene but by a multiple genes present at multiple loci and each one has a small additive effect on the phenotype of  tobacco plant. The additive effect is due to the dominant alleles.

Here 30 cm is the height of plant with genotype aaBbCc and 20 cm is the minimum height of plant i.e plant with genotype aabbcc (homozygous recessive plant).
Thus, two dominant alleles B and C present in plant with genotype aaBbCc give 5 cm per additive (dominant) allele and the height of plant becomes 30 cm from 20 cm.
Now in case of the plant with genotype aabbCc only one additive allele C is present, then the plant will show only 5 cm increase in height from the plant with height of  20 cm.
Hence, the correct answer is 25 cm.

Hope this information will clear your doubts about the height of plant with genotype aabbCc
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