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प्रश्न
Explain the mechanism of hereditary changes.
उत्तर १
Hereditary changes can occur due to the following changes:
- Natural Selection: One allele is fixed for the population as it provides a survival advantage.
- Genetic Drift: Sudden change in a small population due to which genetic variability is reduced.
- Mutations: Sudden and inheritable changes in the genetic material that give rise to a new allele.
- Recombination: When the crossing over occurs during meiosis, the sequence of alleles changes on the chromosomes.
उत्तर २
The mechanism of hereditary changes is as follows:
- Diversity or hereditary changes occur due to genetic variation.
- In sexually reproducing organisms, a fusion of gametes from male and female parents occurs; the offspring always has recombined genes of both the parents. These offspring thus show some characters of either of the parents.
- Also, sometimes sudden changes known as mutations occur in the genes. A change in the position of even a single nucleotide can cause either a minor effect or a considerable alteration in the characters of an individual.
- If these changes (mutations) occur in the DNA of germline cells, then, these changes would be inherited to the next generation.
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संबंधित प्रश्न
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State whether the following statement is true or false :
The sex of an infant is not a case of inheritance of characteristics.
What type of plants were used by Mendel for conducting his experiments on inheritance?
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What is the genotype of tall plants which always produced tall offspring
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For his experiments on heredity, Mendel used :
papaya plants
potato plants
pea plants
pear plants
The following results were obtained by a scientist who crossed the F1 generation of pure-breeding parents for round and wrinkled seeds.
| Dominant trait | Recessive trait | No. of F2 offspring |
| Round seeds | Wrinkled seeds | 7524 |
From these results, it can be concluded that the actual number of round seeds he obtained was ______
Which of the following statement is incorrect?
(a) for every hormone there is a gene
(b) for every protein there is a gene
(c) for production of every enzyme there is a gene
(d) for every type of fat there is a gene
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(a) Bb
(b) bb
(c) BB
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(a) What are A-B type of seeds?
(b) State whether A and B are dominant traits or recessive traits.
(c) What are A-D type of seeds?
(d) What are C-B type of seeds?
(c) Out of A-B and A-D types of seeds, which one will be produced in (i) minimum numbers, and (ii) maximum numbers, in the F2 generation?
Mendel first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea plants having wrinkled-green seeds and found that only round-yellow seeds were produced in the F1 generation. When F1generation pea plants having round-yellow seeds were cross-bred by self pollination, then peas having round-yellow seeds, round green seeds, wrinkled-yellow seeds and wrinkled-green seeds were produced. Mendel collected a total of 2160 seeds.
(a) What will be the number of (i) round green seeds (ii) wrinkled green seeds (iii) round yellow seeds, and (iv) wrinkled-yellow seeds?
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(a) colour of eyes
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(a) deep scar on chin
(b) snub nose
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List two differences in tabular form between dominant trait and recessive traits. What percentage/proportion of the plants in the F2 generation/progeny were round, in Mendel's cross between round and wrinkled pea plants?
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(c) State the type of plants not found in F1 generation but appeared in F2 generation, mentioning the reason for the same.
Mendel, in one of his experiments with pea plants, crossed a variety of pea plant having round seeds with one having wrinkled seeds. State Mendel’s observations giving reasons of F1 and F2 progeny of this cross. Also, list any two contrasting characters, other than round seeds of pea plants that Mendel used in his experiments.
Who is the pioneer of modern genetics?
Write advantages of science of heredity.
In humans, if gene B gives brown eyes and gene b gives blue eyes, what will be the colour of eyes of the persons having combinations
(i) Bb and (ii) BB?
In the following Question, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
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Reason: Traits are independently inherited.
Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be
