Yeast centromeric plasmids (YCp) — defining features Which statements are correct about YCp vectors used in Saccharomyces cerevisiae?
Correct Answer: All of the above
Introduction / Context:YCp vectors were designed to mimic chromosomal behavior by including a yeast centromere (CEN) sequence. This design improves segregation fidelity compared with ARS-only plasmids and reduces copy number to near-chromosomal levels.
Given Data / Assumptions:
- YCp includes a CEN element and typically an ARS for replication.
- CEN confers attachment to the mitotic spindle via kinetochores.
- Faithful segregation occurs in mitosis and, in many cases, meiosis.
Concept / Approach:
Adding a centromere allows the plasmid to assemble a kinetochore and be partitioned like a natural chromosome. As a result, YCp vectors behave as mini-chromosomes: low copy number, relatively stable, and more predictable inheritance than ARS-only plasmids.
Step-by-Step Solution:
Identify presence of centromere: true for YCp.Infer segregation behavior: kinetochore-mediated, high fidelity.Recognize mini-chromosome behavior as a functional description.Therefore, all listed statements are correct.Verification / Alternative check:
Genetic studies show YCp plasmids segregate 1:1 under selection, supporting their chromosome-like behavior.
Why Other Options Are Wrong:
Options a–c are each accurate; rejecting them (option e) contradicts established vector biology.
Common Pitfalls:
Confusing YCp (CEN-containing) with YRp (ARS-only) or YEp (2μm-based), which differ in stability and copy number.
Final Answer:
All of the above