Q.7 In transgenics, alterations in the sequence of nucleotide in genes are due to

P. Substitution
Q. Deletion
R. Insertion
S. Rearrangement

• (A) P and Q
• (B) P, Q and R
• (C) Q and R
• (D) R and S

  Transgenic organisms incorporate foreign DNA, often via random integration causing sequence changes. These mutations—point changes to large shifts—define genetic engineering outcomes. This article solves the MCQ, confirming (B) P, Q and R as the alterations in transgenes.

  Transgenic Integration and Mutations

  In transgenics, DNA microinjection or vectors insert genes into host genomes. Random integration triggers DNA repair, leading to nucleotide alterations at junctions. Substitution (base swap), deletion (nucleotides removed), and insertion (extra bases added) occur during homology-directed repair or non-homologous end joining.

  Correct Answer: (B) P, Q and R
  Transgenic alterations include P. Substitution (e.g., transitions/transversions at insert sites), Q. Deletion (host DNA loss post-integration), and R. Insertion (transgene addition). These modify gene sequences, affecting expression or creating knock-ins.

  Explanation of All Options

  Breakdown of each alteration type in transgenics:

  • P. Substitution
    Valid. Single nucleotide polymorphisms (SNPs) arise from mismatched repair during transgene integration, altering codons (e.g., silent or missense mutations).

  • Q. Deletion
    Valid. Integration excises host sequences; common in CRISPR-assisted transgenics where indels delete bases.

  • R. Insertion
    Valid. Core of transgenesis—foreign DNA inserts, duplicating or adding sequences, often with filler DNA.

  • S. Rearrangement
    Incorrect for nucleotide-level changes. Rearrangements (inversions, translocations) involve large chromosomal shifts, not typical sequence alterations in standard transgenics.

  Code	Alteration Type	Occurs in Transgenics?	Example Mechanism
  P	Substitution	Yes	Base mismatch repair
  Q	Deletion	Yes	NHEJ indels
  R	Insertion	Yes	Microinjection integration
  S	Rearrangement	No	Chromosomal, not nucleotide

  Biotech Implications

  These alterations enable gain/loss-of-function transgenics, like disease models or crop enhancements. For bioinformatics, analyze junctions with BLAST to detect insertions/deletions—vital for your molecular biology projects.