Page 57 - Biology - XII

(c) Law of independent assortment. It states that the inheritance of one factor is independent of the
inheritance of the other factor, i.e. each gene is assorted independently of the other during its
passage from one generation to the another.
1. The traits which follow these laws of Mendel during the inheritance are called as Mendelian traits.
And, the ratios shown are called Mendelian ratios.
2. In monohybrid cross, the phenotypic ratio of F generation is 3 : 1.
2
In dihybrid cross, the phenotypic ratio of F generation is 9 : 3 : 3 : 1.
2

Materials Required
Pea seeds (100 g) and fi ve fl ower pots with soil

Procedure
For spotting steps-1 and 2 are used.
Step-1
1. Separate the pea seeds as follows—
(a) Seeds with smooth or round and wrinkled seeds. Count their numbers and note it.
Step-2

2. Soak the seeds in water for overnight and next day remove the seed coats and note—
(b) The colour of cotyledons—yellow and green. Count their numbers and note it.
3. Note the colour of the seed coat—
(c) Grey seed coat and white seed coat. Count their numbers and note it.
Step-3
4. Sow remaining pea seeds (10 in each pot) in the fl ower pots. Allow them to germinate and grow into
plants till they start fl owering and pod formation. Study for—
(d) Height of plant—Tall and dwarf—measure the height of plants.
(e) Flower position—Axial and terminal.

(f) Pod shape—Infl ated and constricted.
(g) Pod colour—Green and yellow.
(h) Flower colour—Purple and white.
Count their numbers and note it in the observation table.

Observations
Study of analysis of seed samples for Mendelian ratio

Seeds/Plants Number of sample
S. No. Traits of pea seeds/plants studied Ratio
1 2 3 4 5 6 7 8 9 10

1. Round/wrinkled seeds R W R R W W R R W R R=6 W=4

2. Yellow/green cotyledons Y G Y Y Y= G=
3. Grey/white seed coat Grey = White =

4. Tall (2 m)/Dwarf (½ m) plant T T= D=

Conclusion

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