Telomeres end with multiple repeated sequences of the pattern (5′) (TTGGGG)n / (3′) (AACCCC)n, but among options, (1) (5′) (Tn Gy)n / (3′) (Ax Cy)n matches the standard notation where T=Tthymine, G=guanine, A=adenine, C=cytosine. Human telomeres specifically repeat 5′-TTAGGG-3′ on the G-rich strand (3′-AATCCC-5′ complementary), fitting the T/G and A/C pattern generally across eukaryotes.​

Option Analysis

• (1) (5′) (Tn Gy)n / (3′) (Ax Cy)n: Correct—Standard telomere notation: G-rich strand (5′-T/G repeats), C-rich complementary (3′-A/C repeats). Human: TTAGGG/AATCCC; Tetrahymena: TTGGGG/AAACCC; Arabidopsis: TTTAGGG/AATCCC.

• (2) (5′) (Ux Gy)n / (3′) (An Cy)n: Wrong—U=uracil belongs to RNA, not DNA telomeres which use T=thymine.

• (3) (5′) (In Gy)n / (3′) (An Cy)n: Wrong—I=inosine (deaminated base) not found in natural telomere repeats.

• (4) (5′) (In Gy)n / (3′) (Ux Cy)n: Wrong—Combines nonexistent inosine (I) with RNA uracil (U).

Answer: (1).​

Introduction to Telomere Sequence Pattern

Telomeres end with multiple repeated sequences of the pattern (5′) (Tn Gy)n on G-rich strand, (3′) (Ax Cy)n on C-rich strand. Humans: 5,000-15,000 TTAGGG repeats protect chromosome ends from erosion and fusion.

Universal Telomere Repeats Explained

• Human/mammals: 5′-TTAGGG-3’n (G-rich); 3′-AATCCC-5’n (C-rich)

• Yeast: TG(1-3)

• Tetrahymena: TTGGGG/AAACCC
  All follow T-rich/G-rich and complementary A-rich/C-rich pattern, option (1).​

Why Other Options Fail

U=uracil (RNA-specific), I=inosine (rare, modified base)—neither occurs in genomic telomere DNA. Only DNA bases T/A/G/C fit natural repeats.​

GATE Molecular Biology Relevance

Tests telomere structure recognition: TnGy/AxCy notation vs. RNA confusers. Essential for chromosome end-replication problem, telomerase questions.​