MONOHYBRID AND DIHYBRID CROSS [ CLASS XII INHERITANCE AND VARIATION]

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MONOHYBRID AND DIHYBRID CROSS

MONOHYBRID CROSS:  The cross between two homozygous individuals differing in single pair of contrasting trait is the monohybrid cross. eg. TT is crossed with tt to form Tt. Here, Tt is a monohybrid, it is differing for only single pair of contrasting trait.

PHENOTYPIC RATIO OBTAINED IN F2 GENERATION- 3 tall : 1 dwarf

GENOTYPIC RATIO OBTAINED IN F2 GENERATION -  1TT: 2Tt: 1tt

DIHYBRID CROSS:     The cross between two homozygous individuals differing in two pairs of contrasting traits is called dihybrid cross. This cross result in formation of dihybrid in F1 generation.

eg. pea plant with yellow seed color and round shape-YYRR is crossed with pea plant with green seed color and wrinkled shape- yyrr. Offspring formed in F1 is a dihybrid with two pair of contrasting traits- YyRr - yellow round 

PHENOTYPIC RATIO OBTAINED IN F2 GENERATION- 

9 YELLOW ROUND : 3 YELLOW WRINKLED: 3 GREEN ROUND : 1 GREEN WRINKLED

GENOTYPIC RATIO OBTAINED IN F2 GENERATION - 

1 YYRR : 2 YYRr : 1 YYrr : 2 YyRR : 4 YyRr : 2 Yyrr : 1 yyRR : 2 yyRr : 1 yyrr

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