Correct option is A
Polymorphisms in intronic regions of a gene can be used for trait mapping. Even though introns are non-coding regions, they can still influence gene expression through:
- Regulatory elements within introns that affect transcription.
- Splicing variations that impact mRNA processing.
- Linkage disequilibrium, where intronic polymorphisms are linked to causative mutations in exons.
Several molecular markers used in genotyping, such as Single Nucleotide Polymorphisms (SNPs) and Microsatellites (SSRs), often target intronic regions for genetic mapping.
Thus, statement (1) is incorrect, making it the right choice.
Information Booster
Types of Molecular Markers:
- RFLP (Restriction Fragment Length Polymorphism) – Based on DNA fragment size variation due to restriction enzyme digestion.
- SSR (Simple Sequence Repeat) – Short tandem repeats, highly polymorphic.
- SNP (Single Nucleotide Polymorphism) – Single base-pair variations in DNA.
- STMS (Sequence Tagged Microsatellite Sites) – Uses PCR to amplify microsatellite markers.
Dominant vs. Codominant Markers:
- Dominant markers (e.g., RAPD, AFLP) do not distinguish heterozygotes.
- Codominant markers (e.g., RFLP, SSR, SNP) detect both alleles, useful for studying heterozygosity.
Multi-Allelic vs. Bi-Allelic Markers:
- Multi-allelic markers (e.g., RFLPs, SSRs) have multiple variants at a locus.
- Bi-allelic markers (e.g., SNPs) have only two possible alleles per site.
Additional Information
Option (2) Codominant molecular markers can be used to detect heterozygosity (Correct):
- Codominant markers allow detection of both alleles in heterozygotes, unlike dominant markers.
Option (3) STMS and SSRP markers are based on polymorphisms in repetitive DNA sequences (Correct):
- These markers target microsatellites (repeat regions), which are highly variable.
Option (4) RFLPs and SSRs are multi-allelic markers (Correct):
- Both markers have multiple alleles per locus, making them valuable for genetic diversity studies.
