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प्रश्न
"It is possible that a trait is inherited but may not be expressed." Give a suitable example to justify this statement.
उत्तर
Let us take the following example to justify the above statement.
Mendel crossed tall pea plants with short pea plants.
Mendel's Observation
F1 generation contained all tall plants. When F1 generation underwent selfing, the trait that was unexpressed in F1 (short) was observed in some F2 progeny. Thus, both traits, tall and short, were expressed in F2 generation in the ratio 3 : 1.
The above experiment indicates that although both the traits of tallness and shortness were inherited in F1 plants, only the tallness trait was expressed. This shows that traits may not show up in an individual but are passed on to the next generation.
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संबंधित प्रश्न
In one of his experiments with pea plants, Mendel observed that when a pure tall pea plant is crossed with a pure dwarf pea plant in the first generation, F1, only tall plants appear.
(a) What happens to the traits of the dwarf plants in this case?
(b) When the F1-generation plants were self-fertilised, he observed that in the plants of the second generation, F2, both tall plants and dwarf plants were present. Why it happened? Explain briefly.
How did Mendel interpret his results to show that traits may be dominant or recessive? Describe briefly.
Define heredity.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as:
Name the first scientist who studied the inheritance of traits from one generation to the next.
State Mendel's second law of inheritance.
When two parents are crossed, the offspring are referred to as :
recessives
test cross
F1 generation
F2 generation
Select the statements that describe characteristics of genes :
(i) genes are specific sequences of bases in a DNA molecule.
(ii) a gene does not code for proteins.
(iii) in individuals of a given species, a specific gene is located on a particular chromosome.
(iv) each chromosome has only one gene..
The farmers have been cultivating a food plant X for over two thousand years and have produced as many as five entirely different looking vegetables A, B, C, D and E from it.
(a) What could the plant X be?
(b) What are A, B, C, D and E?
(c) What is the process of evolution involved in this example known as?
In the following Question, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
Assertion: When pure breed tall plants are crossed with pure breed short plants, all the plants in F1 progeny are tall. When the tall plants of F1 progeny are crossed, short plants re-appear in F2 progeny.
Reason: Traits are independently inherited.
