Page 4 - 2-Lesson Notes-Accumulation of Variations, Inerited Traits

• When only one character is considered while crossing two organisms, then
such a cross is known as monohybrid cross.
• The ratio of characters, arising out of this cross, at F2 generation is called
monohybrid ratio.
• E.g., If tall plant (TT) is crossed with a dwarf plant (tt), we get 3 tall:1 short
plant at the end of the F2 generation.
• So, 3:1 is monohybrid ratio.
• Here, the height of the plant is considered at a time.
Laws of Mendel associated with Monohybrid cross
Law of Dominance says that a gene has two contrasting alleles and one always
expresses itself in the organism.
It is called the dominant gene and it expresses in any possible combination.
Law of Segregation says that traits get segregated completely during the formation
of gametes without any mixing of alleles.

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