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PinkMonkey Online Study Guide-Biology
7.2 Mendel’s Experiments on Sweet Pea
Selection of the material : Mendel selected garden
sweet pea (Pisum sativum) for his hybridization experiments for
of the following reasons : (i) Plants are annual and easy to cultivate.
(ii) Peas have many distinct, well-defined and easily observable morphological
characteristics (traits). (iii) Flowers are bisexual and naturally self-fertilizing,
but they can also be easily cross-fertilized. (iv) The offspring of cross-fertilized
plants are fertile. (v) Flowers are sufficiently large for easy emasculation
(removal of stamens) and artificial cross-pollination.
Selection of characters (traits) : Mendel selected
14 different varieties of the pea and grouped them into seven pairs.
Each pair was considered for a specific trait (characteristic)
such as flower color or seed shape or stem length, etc. The two
members of each pair showed contrasting forms of the chosen trait,
,e.g., in a pair selected for stem length, one variety had a tall
stem (6-7 feet tall) while the other had a dwarf stem . These
seven pairs of contrasting traits are shown in Table 1.1.
Table 1.1 : Showing seven pairs of contrasting characters
selected by Mendel
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Sr. No.
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Characters
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Contrasting pairs (Allelic pairs)
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(Dominant)
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(RecBIOe)
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BIOBIOBIO |
1.
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Form of seed
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Round (R)
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Wrinkled(r)
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2.
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Color of cotyledons
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Yellow(Y)
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Green(y)
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3.
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Color of seed coat
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Colored(C)
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White(c)
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4.
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Form of pod
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Inflated (I)
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Constricted(i)
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5.
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Color of pod
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Green(G)
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Yellow(g)
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6.
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Position of flower
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Axial(A)
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Terminal(a)
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7.
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Height of plant (Length of stem)
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Tall(T)
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Dwarf(t)
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Nature and procedure of the experiments : Mendel
had very clear concepts of what he was doing and what requirements were
necessary if he had to arrive at the conclusions accurately and successfully.
He realized the necessity of: (i) using pure breeding parent plants; (ii)
considering only one character at a time during the breeding experiments;
(iii) always keeping the generations separate; (iv) and using statistical
and mathematical principles to compute the obtained results properly.
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