The following gel patterns are DNA markers observed in parents (P1 and P2), F₁ progeny from a cross between them, and doubled haploid (DH) progeny (panel A) or F₂ progeny (panels B and C), derived from selfing of F₁.

A doubled haploid (DH) is a genotype formed when plants are developed from haploid cells that have undergone chromosome doubling.

Based on the pattern observed in the DH or F₂ progeny, identify which of the patterns (A to C) are based on DNA markers that are allelic.​

Correct option is D

To determine which DNA markers are allelic, we analyze how segregation patterns appear in DH and F₂ progeny.

Understanding DH and F₂ Progeny Segregation Patterns:

1. Doubled Haploid (DH) Progeny:

   • DH plants are produced from haploid gametes that undergo chromosome doubling.
   • Since haploid cells contain one allele per locus, allelic markers segregate as fixed homozygous bands.

2. F₂ Progeny:

   • F₂ plants result from selfing F₁, so they follow Mendelian segregation (1:2:1 or 3:1 ratios).
   • If a DNA marker is allelic, the bands should segregate in an expected ratio of homozygous and heterozygous patterns.

Analyzing the Gel Patterns:

• Panel A (DH Progeny):

  • The DH lines show only one of the parental alleles per individual, which is characteristic of allelic markers.
  • Thus, Panel A markers are allelic.

• Panel B (F₂ Progeny):

  • The F₂ progeny show Mendelian segregation of bands.
  • Such segregation is characteristic of allelic markers.
  • Thus, Panel B markers are allelic.

• Panel C (F₂ Progeny):

  • The banding pattern in F₂ does not follow clear Mendelian segregation.
  • This suggests that Panel C markers are non-allelic (likely dominant markers or multi-locus markers).

Final Conclusion:

A and B are based on allelic markers, while C is not.
Correct Answer: Option 4 (A and B).

Information Booster

1. Allelic markers are genetic variants at the same locus that segregate in expected Mendelian ratios.
2. Doubled haploid (DH) plants are homozygous for all loci, making them useful for identifying allelic markers.
3. F₂ progeny segregate in Mendelian ratios, which helps confirm whether markers are allelic.
4. Non-allelic markers include multi-locus markers (e.g., dominant markers like RAPDs or ISSRs) that do not segregate in a Mendelian fashion.
5. Codominant markers (e.g., SSRs, SNPs) are useful for distinguishing alleles at a single locus.