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प्रश्न
Short Answer Question.
Write a note on pleiotropy.
Give an account of pleiotropy with a suitable example.
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उत्तर
- When a single gene controls two (or more) different traits it is called pleiotropic gene and the phenomenon is called pleiotropy or pleiotropism.
- The phenotypic ratio is 1: 2 instead of 3: 1 because of the death of recessive homozygote.
- For example, the disease, sickle-cell anaemia, is caused by a gene HbS. Normal or healthy gene HbA is dominant.
- The carriers (heterozygotes HbA /HbS) show signs of mild anaemia as their RBCs become sickle-shaped i.e. half-moon-shaped only under abnormally low O2 concentration.
- The homozygotes with recessive gene HbS die of fatal anaemia.
- Thus, the gene for sickle-cell anaemia is lethal in homozygous conditions and produces sickle cell trait in the heterozygous carrier. Two different expressions are produced by a single gene.
Graphical representation of pleiotropy - A marriage between two carriers will produce normal, carriers and sickle-cell anaemic children in a 1: 2: 1 ratio.
संबंधित प्रश्न
Which genes show straight inheritance?
The genotypes of a husband and wife are IAIB and IAi respectively. How many different genotypes and phenotypes are possible among the blood types of their children?
______ becomes half-moon-shaped in a person suffering from sickle cell anaemia.
______ refers to a phenomenon in which heterozygotes have features of both the homozygotes, that is, an allele is neither dominant nor recessive to the other.
Calculate the the birth rate of cattle per year in a dairy farm; where there were a total of 45 cattles previously. 5 new offsprings were added due to reproduction taking the total population to 50.
In which of the following, are the genotypic and phenotypic ratios are same?
Which idea is depicted by a cross in which the F1 generation resembles both the parents?
If a red flowered Mirabilis jalapa plant is crossed with a white flowered plant, what will be the phenotypic ratio in F2 generation? Show it by a chart.
Fill in the blanks:
| Column 'A' (Gene interactions) |
Column 'B' (Example) |
|
| (1) | Co-dominance | ______ |
| (2) | Incomplete dominance | ______ |
| (3) | Multiple allelism | ______ |
| (4) | Pleiotropy | ______ |
| (5) | Polygenes | ______ |
| (6) | Autosomal dominance | ______ |
A pea plant homozygous for yellow round seed is crossed with its recessive parents. Calculate the phenotypic and genotypic ratio with the help of a checkerboard.
