Which statement is false about yeast artificial chromo- somes (YACs)?

Options

A. They are used to clone DNA fragments of more than 1 Mb in size
B. They have been exploited extensively in mapping the large genomes like in human genome project
C. They contain telomeric sequence, the centromere and autonomously replicating sequence from yeast chromosomes
D. They have cos sites

Answer

### Step-by-Step Solution:

1. **Understanding Yeast Artificial Chromosomes (YACs)**:
- YACs are engineered DNA molecules derived from the yeast species *Saccharomyces cerevisiae*. They are designed to clone large DNA fragments.

2. **Evaluating the Statements**:
- **Statement 1**: "They are used to clone DNA fragments of more than 1 MB in size."
- YACs can clone DNA fragments ranging from 100 KB to 1 MB. Since 1 MB is equal to 1000 KB, this statement is true as YACs can handle fragments up to 1 MB.

- **Statement 2**: "They have been exploited extensively in mapping the large genomes like in Human Genome Project."
- YACs are indeed used in mapping and sequencing large genomes, including the Human Genome Project. This statement is also true.

- **Statement 3**: "They contain telomeric sequence, the centromere and autonomously replicating sequence from yeast chromosomes."
- YACs do contain telomeric sequences, centromeres, and autonomously replicating sequences (ARS) derived from yeast chromosomes. Therefore, this statement is true.

- **Statement 4**: "They have cos sites."
- This statement is false. YACs do not contain cos sites; cos sites are characteristic of cosmid vectors, not YACs.

3. **Conclusion**:
- The false statement about yeast artificial chromosomes (YACs) is that they have cos sites.

### Final Answer:
The false statement about yeast artificial chromosomes (YACs) is: **"They have cos sites."**

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