Q.4 Yeast artificial chromosomes (YAC’s) are used for cloning

• (A) large segments of DNA
• (B) mRNA
• (C) bacterial DNA
• (D) yeast DNA
  

  Yeast Artificial Chromosomes (YACs) Are Used for Cloning

  Yeast artificial chromosomes (YACs) are used for cloning large DNA segments in yeast cells, revolutionizing genomics and genetic engineering. This SEO-optimized article tackles the MCQ: Yeast artificial chromosomes (YACs) are used for cloning (A) large segments of DNA, (B) mRNA, (C) bacterial DNA, or (D) yeast DNA—perfect for biotechnology students studying molecular biology and cloning vectors.

  Correct Answer: Option (A) Large Segments of DNA

  Yeast artificial chromosomes (YACs) are used for cloning large segments of DNA, typically 100-1000 kb or more, mimicking natural chromosomes with elements like centromeres, telomeres, and ARS for stable replication in yeast.

  Developed in 1987, YACs enable genome mapping (e.g., Human Genome Project) by handling fragments too big for plasmids (up to 10 kb) or cosmids (40 kb), aiding gene discovery in bioengineering.

  Explanation of All Options

  Understanding vector capacities clarifies why YACs excel in large-scale cloning.

  • (A) Large segments of DNA: Correct. YACs accommodate 200 kb to 2 Mb inserts, ideal for eukaryotic genomes and physical mapping via chromosome walking.

  • (B) mRNA: Incorrect. mRNA requires cDNA synthesis for cloning into expression vectors like plasmids; YACs aren’t suited for small, unstable RNA-derived sequences.

  • (C) Bacterial DNA: Incorrect. Bacterial DNA uses BACs or plasmids; YACs target eukaryotic large fragments, though bacterial elements aid propagation.

  • (D) Yeast DNA: Incorrect. While hosted in yeast, YACs clone exogenous large DNA, not native yeast sequences primarily.

  Option	Typical Insert Size	Primary Use Case	Correct/Incorrect
  (A) Large segments of DNA	100 kb – 2 Mb	Genome mapping, large genes	Correct
  (B) mRNA	<10 kb (cDNA)	Expression libraries	Incorrect
  (C) Bacterial DNA	<50 kb	Bacterial vectors (BACs)	Incorrect
  (D) Yeast DNA	Variable	Yeast plasmids (YEp/YIp)	Incorrect

  Applications in Biotechnology

  YACs support genetic engineering, functional genomics, and microbial studies, aligning with fermentation and enzyme kinetics research. Despite instability issues, they paved the way for BACs in modern sequencing.