Modern genetic techniques allow scientists to determine the arrangement and relative positions of genes, that is DNA sequences, on a chromosome. How does this knowledge benefit society? Consider the following statements and choose the correct combination.

Introduction / Context:
This question deals with gene mapping and the practical benefits of knowing the positions of genes on chromosomes. It uses three statements to test whether you can distinguish realistic applications of genetic information from exaggerated claims, especially in the context of livestock breeding and disease understanding.

Given Data / Assumptions:
• Statement 1: It is possible to know the pedigree and ancestry of livestock using genetic information.
• Statement 2: It is possible to understand the causes of all human diseases using gene maps.
• Statement 3: It is possible to develop disease resistant animal breeds using genetic knowledge.
• We must select which combination of statements is correct.

Concept / Approach:
Gene mapping allows identification of markers and genes associated with particular traits, including diseases, productivity and ancestry. This definitely helps trace pedigrees and design breeding programmes, making statements 1 and 3 realistic. However, statement 2 is too absolute because not all human diseases are purely genetic; many have environmental, lifestyle or infectious causes. Even for genetic diseases, current knowledge is incomplete. Therefore, it is incorrect to claim that mapping alone allows us to understand the causes of all human diseases.

Step-by-Step Solution:
Step 1: Evaluate statement 1. Genetic markers inherited from parents can be used to reconstruct family trees and pedigrees in livestock. Step 2: Recognise that this is widely done in animal breeding programmes, so statement 1 is correct. Step 3: Examine statement 2, which uses the word all for human diseases. Step 4: Understand that many human diseases have complex, multifactorial causes, including environmental and infectious factors, so mapping genes alone does not explain all of them. Step 5: For statement 3, note that once genes linked to disease resistance are known, breeders can select animals with favourable alleles to develop disease resistant breeds, making statement 3 correct. Step 6: Combine the analysis and conclude that statements 1 and 3 only are correct.

Verification / Alternative check:
Examples from dairy cattle and poultry breeding programmes show that marker assisted selection based on known gene positions is used to improve resistance to certain diseases and to track pedigrees. At the same time, public health discussions emphasise that lifestyle diseases such as obesity and many infections cannot be fully explained by gene maps alone, which confirms that statement 2 is overstated and therefore incorrect.

Why Other Options Are Wrong:
1 and 2 only: Includes statement 2, which is too absolute about all human diseases and therefore incorrect.
2 only: Ignores the clearly valid uses in pedigree analysis and breeding and also relies on the exaggerated claim about all diseases.
1, 2 and 3: Again includes statement 2, so this combination cannot be correct even though 1 and 3 are true.
3 only: Ignores the obvious benefit of using genetic markers to reconstruct pedigrees and ancestry in livestock populations.

Common Pitfalls:
A common trap is to be impressed by the power of modern genetics and assume that it can explain every disease without limitation. Examination questions often use words like all or always as a signal to check carefully whether the claim is overgeneralised. Train yourself to look for such absolute words and verify if the statement is realistic in scientific terms before deciding.

Final Answer:
The correct combination of statements is 1 and 3 only, meaning gene mapping helps in tracing livestock pedigree and in developing disease resistant animal breeds, but it does not yet explain the causes of all human diseases.