Human chromosome 1 in mouse immortal cell background

Telomeres are specialized structures at the ends of linear chromosomes and are essential for normal cellular function. Telomeres prevent degradation and aberrant recombination of chromosome termini and facilitate appropriate replication of chromosome ends. In this work, the telomere dynamics was followed in the immortal mouse cell strain A9 in comparison with A9+1. The latter is derived from A9 cells by introduction of human chromosome 1. In spite of the telomerase presence, a great decrease in telomere lengths was noticed in A9+1 compared to A9 cells. Behavior of individual human and mouse telomeres was also followed under the conditions of the observed gross telomere shortening. Human chromosome I followed the overall telomere length in hybrid cells. It is suggested that telomere lengths are primarily determined by the cell protein background.