Lecture 6 - Growing up and growing old
Hydra can regenerate a head when it is removed but this does not require growth. However, growth is required when newts regenerate their limbs. A model for regeneration based on a polar coordinate system can explain why extra limbs grow out when a cockroach leg is rotated 180°.
Growth is programmed very early - our two arms when they are just a few millimetres long - and after 18 years of growth they are the same length. Yet their growth is quite independent of each other. Our overall growth is controlled by hormones. If there is too little growth hormone then a dwarf will result, too much, a giant. The main sexual differences between men and women are due to male hormones acting on the tissues. Basically we are all female, but males develop because the Y chromosome causes the development of a testis and so male hormones are made. Differences in the timing of growth can alter the form of animals - the giant antlers of the Irish Elk may just be due to extending the growth period.
Ageing can be thought of in terms of wear and tear and the running out of the developmental programme. Normal skin cells can only divide a finite number of times in culture. There has, over the last century, been an increase in the number of people reaching old age, but no increase in life-span. Can this be altered? Why is mouse tissue old at the same age at which an elephant is born? Will Frankenstein ever be able to make his angel immortal?
About the 1986 CHRISTMAS LECTURES
In the 1986 CHRISTMAS LECTURES, Professor Lewis Wolpert (1929-2021) explores developmental biology in a series titled 'Frankenstein's Quest'. Quoting the fictional Dr Frankenstein: "After days and nights of incredible labour and fatigue, I succeeded in discovering the cause of generation and life..." These lectures will look at how life really is generated.
All life comes from cells and all the animals we see about us come from just one cell, the fertilized egg. How does the egg give rise to bats and boys, gnats and girls, eyes and arms? The egg divides and gives rise to many cells which move, multiply, change, and communicate, and from these activities animals emerge through embryonic development. Like an imaginary Frankenstein, we will explore what we need to know in order to control development in order to create not a monster, but an angel.