- Given below are a few statements related to biological principles and/or techniques:
A. Genetic diversity plays an important role in the identification of combiners for heterosis breeding
B. Genotyping by sequencing (GBS) can be used to identify allelic diversity but is not useful for
construction of linkage maps.
C. Genome editing by sequence specific nucleases (SSNs) in the presence of guide RNAs would result in NHEJ-mediated knock outs and loss of function mutations.
D. In a comparison of synteny and colinearity between diploid and polyploid plant genomes, colinearity is high but synteny is low.
Which one of the following options represents all correct statements?
(1) A and C only (2) B and D only
(3) A, C and D (4) B onlyStatement-wise explanation
A. Genetic diversity and heterosis – Correct
High genetic diversity among parental lines helps identify good combiners that produce strong heterosis (hybrid vigour) because diverse alleles interact in the F₁ to enhance performance.
So, genetic diversity indeed “plays an important role in the identification of combiners” → A is correct.B. GBS and linkage maps – Incorrect
The statement says GBS “is not useful for construction of linkage maps.”
In reality, genotyping‑by‑sequencing (GBS) is routinely used to discover thousands of SNPs and to build high‑density genetic linkage maps in many crops.
So B is false.C. SSNs, guide RNAs and NHEJ knockouts – Correct
Sequence‑specific nucleases such as CRISPR–Cas, TALENs, or ZFNs, guided to a target sequence, create a double‑strand break.
In the absence of a repair template, the break is repaired by non‑homologous end joining (NHEJ), which often introduces small insertions/deletions causing frameshifts or premature stops → loss‑of‑function (knockout) mutations.
Thus C is correct.D. Synteny and colinearity in diploid vs polyploid genomes – Incorrect
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Synteny: conservation of gene content and approximate order on chromosomes between species/genomes.
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Colinearity: more detailed conservation of gene order and orientation within syntenic blocks.
In many diploid–polyploid comparisons, both synteny and colinearity are generally high, not “synteny low, colinearity high.”
If synteny were low (few shared blocks), high colinearity would not be observed genome‑wide.
Therefore D is incorrect.
Answer choice
Only A and C are correct, so the right option is (1) A and C only.
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