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प्रश्न
Explain the mechanism of hereditary changes.
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उत्तर
- 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
How do Mendel's experiment show that traits are inherited independently?
A pea plant with blue colour flower denoted by BB is cross-bred with a pea plant with white flower denoted by ww.
(a) What is the expected colour of the flowers in their F1 progeny?
(b) What will be the percentage of plants bearing white flower in F2 generation, when the flowers of F1 plants were selfed?
(c) State the expected ratio of the genotype BB and Bw in the F2 progeny.
Name the information source for making proteins in the cells.
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:
To perform an experiment to identify the different parts of an embryo of a dicot seed, first of all you require a dicot seed. Select dicot seeds from the following group:
Wheat, Gram, Maize, Pea, Barley, Ground-nut
(A) Wheat, Gram and Pea
(B) Gram, Pea and Ground-nut
(C) Maize, Pea and Barley
(D) Gram, Maize and Ground-nut
What type of plants were used by Mendel for conducting his experiments on inheritance?
Fill in the following blank with suitable word .
In pea plants, the gene for dwarfness is ..............whereas that for tallness is ............ .
Using height (tallness/dwarfness) of a plant as an example, show that genes control the characteristics or traits in an organism.
It it an example of monohybrid cross or dihybrid cross?
What is the genotype of (i) dwarf plants, and (ii) tall plants, whose parental cross always produces tall offspring?
Gregor Mendel's first law of genetics states "Of a pair of contrasted characters, only one can be represented in a gamete by its internal 'factor Give the modern name for this 'factor'.
Give the contrasting traits of the following characters in pea plant and mention which is dominant and which is recessive:
Yellow seed
How do Mendel's experiments show that traits may be dominant or recessive?
When two parents are crossed, the offspring are referred to as :
recessives
test cross
F1 generation
F2 generation
A cross between two individuals results in a ratio of 9 : 3 : 3 : 1 for four possible phenotypes of progeny. This is an example of a ______
In the human blood grouping, the four basic blood types are type A, type B, type AB, and type O. The blood proteins A and B are :
(a) simple dominant and recessive traits
(b) incomplete dominant traits
(c) codominant traits
(d) sex-linked traits
A pregnant woman has an equal chance of her baby being blood group A or blood group AB. Which one of the following shows the possible genotypes of the woman and the father of her child?
(a) IA IA and IB IO
(b) IA IB and IB IO
(c) IA IO and IB IO
(d) IA IB and IA IO
The visible characteristic in an organism is known as :
(a) prototype
(b) stereotype
(c) phenotype
(d) genotype
A cross between a tall plant (TT) and short plant (tt) resulted in progeny that were all tall plants because :
(a) tallness is the dominant trait
(b) shortness is the dominant trait
(c) tallness is the recessive trait
(d) height of plant is not governed by gene T or t
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
If the ratio of each phenotype of the seeds of pea plants in the F2 generation is 9 : 3 : 3 : 1, it is known as :
(a) tetrahybrid ratio
(b) monohybrid ratio
(c) dihybrid ratio
(d) trihybrid ratio
Pure-bred pea plants A are crossed with pure-bred pea plants B. It is found that the plants which look like A do not appear in F1 generation but re-emerge in F2 generation. Which of the plants A and B are : (i) tall, and (ii) dwarf? Give reason for your answer.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits-blood group A or O - is dominant? Why or why not?
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?
(b) Which 'ratio' as established by Mendel have you made use of in answering the part (a) above?
Only one of the following characteristic of the parents can be inherited by their children. This one is :
(a) deep scar on chin
(b) snub nose
(c) technique of swimming
(d) cut nose
One of the following traits of the parents cannot be passed on to their future generations. This trait is :
(a) cleft chin
(b) pointed chin
(c) scarred chin
(d) broad chin
"It is possible that a trait is inherited but may not be expressed." Give a suitable example to justify this statement.
If we pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F1 generation. If we now self-cross the pea plant of F1 generation, then we obtain pea plants of F2 generation.
(a) What do the plants of F2 generation look like?
(b) State the ratio of tall plants to dwarf plants in F2 generation.
(c) State the type of plants not found in F1 generation but appeared in F2 generation, mentioning the reason for the same.
Explain Mendel’s law of independent inheritance. Give one example.
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.
Define Heredity. Give two examples.
Answer the following question.
Why are the traits acquired during the life-time-of-an individual not inherited? Explain.
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?
A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because
What are the components of the DNA molecule?
A cross between pea plant with white flowers (vv) and pea plant with violet flowers (VV) resulted in F2 progeny in which ratio of violet (VV) and white (vv) flowers will be ______.
Name the following:
The basic units of heredity.
