Cat Cloning and Other Technologies

by Sarah Hartwell

Chronological Age and Biological Age

Chronological age (calendar age) is the time elapsed from date of birth to present day. In normally conceived animals, the chronological age is what we refer to simply as "age" - the number of years we have existed, the number of birthdays we have celebrated.

Biological age is the cellular age (as described above). For normally conceived animals the biological age is the same as the chronological age. For clones, it is the chronological age of the clone plus the chronological age of the donor at the point where the cell was extracted (not counting any time that the cell spent frozen before being transferred into an egg). So if the donor animal was 5 years old when its cell was taken, then the clone's biological age will be its chronological age PLUS 5 years.

The impact of this is that the cells are older than the organism in which they reside. They are likely to suffer the effects of ageing at the normal time in biological terms (i.e. when the cell donor would show these signs), though this would be premature ageing in terms of the clone's chronological age! In simple terms, the clone may be a newborn, but it is built out of old cells! It is like buying what appears to be a new car and discovering it has an old engine inside; it will run down quicker.

If a clone was to be cloned, the biological age would be the biological age of the original donor when the cell was extracted PLUS the biological age of the clone when ITS cell was extracted plus the chronological age of the clone of the clone! This would put a practical limit on the further cloning of clones.

Unless a way is found to reverse the cell's ageing process and reset its internal clock to zero, clones can reasonably be expected to live less long than normally conceived animals and to show age-related degenerative conditions earlier than normally conceived animals.