Sensitive method for measuring telomere lengths by quantifying telomeric DNA content of whole cells

Recently, a new method for measuring telomere lengths based on telomere DNA content was developed. The method, which is based on the ratio of telomere to centromere DNA content (TC ratio), is highly sensitive, allowing the an alysis of small quantities of DNA. However, the method required the isolati on of DNA, which can be difficult or impossible for small numbers of cells. Here, we suggest an improvement of this method that can directly estimate telomere lengths from whole cells. We optimized the method for whole cells and purified DNA and found that accurate TC ratios can be obtained from as little as 9 ng of DNA or 800 whole cells. There was no statistically signif icant difference between the ratios obtained with purified DNA or with whol e cells, indicating that the isolation of DNA is not necessary for small sa mples.