Raju and Rani are planning a family, but sas each has a brother having the sickle-cell disorder, they are worried that their kids might develop the disorder too. Neither Raju, Rani nor their respective parents have the disorder. They decide to consult a genetic counsellor who conveys them this

The correct option is: "its is possible that none of their kids will have the disorder, but blood tests on both of them should be carried out to confirm"

Let us understand the genetics of sickle-cell disorder and analyze the scenario step-by-step to see why this option is correct.

1. Understanding the Mode of Inheritance:
Sickle-cell disorder is an autosomal recessive genetic condition. This means that a person must inherit two copies of the mutated gene (one from each parent) to express the disorder. Let:
- A represent the normal allele (dominant)
- s represent the sickle-cell allele (recessive)
A person with genotype AA is completely normal. A person with genotype As is a carrier (healthy but carries the trait). A person with genotype ss has the sickle-cell disorder.

2. Analyzing the Parents (Raju and Rani):
Neither Raju, Rani, nor their respective parents have the disorder. This means none of them are ss.
However, both Raju and Rani have a brother who has the sickle-cell disorder (genotype ss).
For their brothers to be ss, both of Raju's parents must have contributed an s allele, and both of Rani's parents must have also contributed an s allele. Since the parents themselves do not have the disorder, they must be carriers (genotype As).

3. Determining the Carrier Probability for Raju and Rani:
Since Raju's parents are both carriers (As × As), the possible genotypes for their offspring are:
AA, As, As, and ss.
Since we already know that Raju does not have the disorder, we can exclude the ss genotype. Therefore, Raju has a 2/3 chance of being a carrier (genotype As) and a 1/3 chance of being homozygous normal (genotype AA).
The exact same probability applies to Rani; she also has a 2/3 chance of being a carrier (genotype As).

4. Why None of Their Kids Might Have the Disorder:
- If either Raju or Rani (or both) is homozygous normal (AA), none of their children can inherit two recessive alleles (ss). In this case, 0% of their children will have the disorder.
- Even if both Raju and Rani are carriers (As × As), the chance of any child inheriting the disorder (ss) is 1/4 (25%), meaning there is a 3/4 (75%) chance that each child will be healthy (either AA or As). Therefore, it is entirely possible that none of their kids will have the disorder.

5. Why Blood Tests are Crucial:
Because Raju and Rani do not exhibit symptoms, we cannot know their genotypes (whether they are AA or As) without performing genetic or blood testing (such as hemoglobin electrophoresis). If the tests show that at least one of them is AA, they can be reassured that their children will not have the disease. If both are carriers (As), they can receive appropriate counseling regarding the risk of transmission. Therefore, blood tests should be carried out on both of them to confirm their carrier status.