Animal Genetics and Breeding- ICAR JRF/SRF 2024

• Bovine Genome Sequencing Consortium Publication: The draft sequence and analysis of the domestic cattle (Bos taurus) genome was published in the journal Science in April 2009 (Vol. 324, Issue 5926, pp. 522–528) by the Bovine Genome Sequencing and Analysis Consortium.
• Key Findings:
• Sequenced the genome of a Hereford cow named L1 Dominette 01449.
• Genome size of $\sim 2.87$ billion base pairs with at least 22,000 protein-coding genes.
• Revealed evolutionary changes in immune and lactation genes, laying the foundation for modern genomic selection in dairy and beef cattle.

Correct option: (4) 2009

• Central Dogma of Molecular Biology: Proposed by Francis Crick in 1958 (and reaffirmed in Nature in 1970).
• Core Principle: Explains the directional, irreversible flow of sequential genetic information in biological systems:

• Postulate: Once "information" has passed into protein, it cannot get out again (protein sequence cannot direct nucleic acid synthesis).

Correct option: (2) Francis Crick

• Recommended DNA Markers for Animal Genetic Diversity: Joint recommendations by FAO and ISAG (International Society for Animal Genetics) for evaluating livestock biodiversity, genetic distance, and breed structure:
• Microsatellites / STRs (C): Highly polymorphic, codominant, abundant across the genome, and standardized internationally for pedigree verification and diversity panels.
• Single Nucleotide Polymorphisms - SNPs (B): High-density, biallelic codominant markers with high throughput and automated genotyping arrays (e.g., 50K and 770K bovine chips).
• Other Markers:
• RFLP (A) and Minisatellites (D) were legacy early-generation markers now largely superseded due to lower throughput and technical complexity.

Correct option: (1) (B) and (C) only.

• Assertion (A) is True: Sewall Wright's fixation index ($F_{ST}$) is the standard metric used in population genetics to measure genetic differentiation and population substructure among populations:

where $H_T$ is total expected heterozygosity and $\bar{H}_S$ is mean within-subpopulation heterozygosity.

• Reason (R) is True: $F_{ST}$ quantifies the proportion of total genetic variance attributable to differences between subpopulations:
• $F_{ST} = 0$: Indicates panmixia (no genetic differentiation; complete allele frequency sharing).
• $F_{ST} = 1$: Indicates complete fixation and divergence for alternative alleles.
• Explanation: (R) defines the mathematical and biological foundation that makes $F_{ST}$ a valid diversity measure.

Correct option: (1) Both (A) and (R) are true and (R) is the correct explanation of (A)