Advertisements
Advertisements
Question
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?
Solution 1
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.
Solution 2
- 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.
APPEARS IN
RELATED QUESTIONS
"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.
How did Mendel interpret his results to show that traits may be dominant or recessive? Describe briefly.
Mendel crossed tall pea plants with dwarf pea plants in his experiment. Write his observations giving reason on the F1 and F2 generations.
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 Mendelian experiment consisted of breeding pea plants bearing violet flowers with pea plants bearing white flowers. What will be the result in F1 progeny?
Mendel said that the characteristics or traits of organisms are carried from one generation to the next by internal factors which occur in pairs. What is the modern name for these factors?
Fill in the following blank with suitable word .
In pea plants, the gene for dwarfness is ..............whereas that for tallness is ............ .
It it an example of monohybrid cross or dihybrid cross?
Give the contrasting traits of the following characters in pea plant and mention which is dominant and which is recessive :
Round seed
What are the units of heredity.
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
Explain the mechanism of hereditary changes.
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.
What is genetics?
Write advantages of science of heredity.
If a tall pea plant is crossed with a pure dwarf pea plant then, what percentage of F1 and F2 generation respectively will be tall?
