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प्रश्न
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?
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उत्तर १
No. This information is not sufficient to determine which of the traits – blood group A or O – is dominant. This is because we do not know about the blood group of all the progeny.
Blood group A can be genotypically AA or AO. Hence, the information is incomplete to draw any such conclusion.
उत्तर २
- If blood group A is dominant: The mother would be homozygous for the recessive allele O. The father, with blood group A, could be either homozygous or heterozygous. If he is homozygous, he would not carry the allele O. The daughter would inherit allele O only from her mother, but since allele O is recessive, it would not be expressed. However, if the father is heterozygous, he would also have an allele for O. In this case, the daughter could inherit allele O from both parents and if homozygous for the recessive allele O, she would have blood group O.
- If blood group O is dominant: The father would lack allele O in order to have blood group A. The mother could be either homozygous or heterozygous for allele O. In both situations, the daughter would inherit one allele for blood group O, and since allele O is dominant, it would always be expressed, resulting in the daughter having blood group O.
Thus, since the daughter could have blood group O in both scenarios, we cannot definitively say which blood group is dominant.
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संबंधित प्रश्न
"A trait may be inherited, but may not be expressed." Justify this statement with the help of a suitable example.
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.
In a monohybrid cross between tall pea plants (TT) and short pea plants (tt), a scientist obtained only tall pea plants (Tt) in the F1 generation. However, on selfing the F1 generation pea plants, he obtained both tall and short plants in F2 generation. On the basis of above observations with other angiosperms also, can the scientist arrive at a law? If yes, explain the law. If not, give justification for your answer.
What is a gene?
List any two contrasting characters other than roundness of pea plants that Mendel used in his experiments with pea plants.
Outline a project which aims to find the dominant coat colour in dogs.
A man having blood group O marries a woman having blood group B and they have a daughter. What will be the blood group of the daughter?
What will you get in the F1 and F2 generations in the following cross?
Pure tall pea plant × Pure dwarf pea plant
In the F2 generation of a cross, progeny having different traits are produced in the ratio 3 : 1. State whether it is a monohybrid cross or a dihybrid cross? Give one example of such a cross.
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' State where these factors are found in gametes.
State Mendel's second law of inheritance.
For his experiments on heredity, Mendel used :
papaya plants
potato plants
pea plants
pear plants
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
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
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 the following combination of genes?
(a) Bb
(b) bb
(c) BB
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?
One of the following traits of the parents cannot be passed on to their future generations. This trait is:
Define Heredity. Give two examples.
What will be the number of chromosomes present in each gamete produced by the plants if the palisade cells of a species of the plant contain 28 chromosomes in all?
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.
