57. In recent decades.the use of genetic markers has allowed the rapid introgression and selection of desired breeding stocks in advance generations. In this regard, following statements are given:
A. AFLP markers can discriminate between homozygote and heterozygote genotypes.
B. Microsatellites (eg. SSR) are capable of detecting higher level of polymorphism than RFLP.
C. SNPs are more prevalent in the coding regions of the genome.
D. SNP markers are the most suitable markers for bothforeground and background selection.
Which one of the following combination of the above statements is correct?
(1) A, B and C (2) A, B and D
(3) B and C only (4) B and D only
Question Overview
Genetic markers enable rapid introgression and selection of breeding stocks in advanced generations, crucial for plant breeding efficiency. The query evaluates statements on AFLP, SSR (microsatellites), SNP, and RFLP markers. Correct combination identifies B and D only, making option (4) the answer.
Statement Analysis
A. AFLP Markers Homozygote Heterozygote Discrimination
AFLP (Amplified Fragment Length Polymorphism) markers are dominant, scoring presence/absence of bands, thus cannot reliably discriminate homozygotes from heterozygotes without specialized equipment like gel scanners. Standard AFLP application treats them as dominant, failing routine heterozygote detection unlike codominant markers (e.g., SSR, RFLP). Statement A is incorrect.
B. SSR Higher Polymorphism than RFLP
Microsatellites (SSR) detect higher polymorphism levels than RFLP due to multi-allelic nature from repeat length variations, offering greater resolution in genetic diversity studies. SSRs excel in breeding for their hypervariability versus RFLP’s biallelic restrictions. Statement B is correct.
C. SNPs Prevalent in Coding Regions
SNPs predominate in non-coding regions (introns, intergenic) due to stronger purifying selection in coding exons, with lower rates and periodicity in codons (highest at wobble position). Over 90% of trait-associated SNPs occur non-coding. Statement C is incorrect.
D. SNP Suitability for Foreground Background Selection
SNP markers excel in foreground (target QTL tracking) and background (recurrent parent genome recovery) selection owing to abundance, genome-wide coverage, codominance, and high-throughput genotyping. They accelerate introgression breeding over multi-locus markers like AFLP. Statement D is correct.
Correct Option
Option (4) B and D only matches verified properties of genetic markers introgression selection. This aligns with marker-assisted selection principles in advanced breeding stocks.
