Cloning and protecting the environment

In 1997, scientists in Scotland made a sheep whose genes came entirely from another sheep's body cell, not from an egg and sperm.

A clone is a cell or individual and all its asexually produced offspring, genetically identical except when a mutation occurs. Some insects and plants clone naturally, but most animals do not.

To make Dolly, scientists removed the nucleus from a fertilized egg and inserted a nucleus from a body cell of a grown sheep. The altered egg was implanted in a womb to develop, becoming a clone of the nucleus donor.

A second method splits one early embryo into separate embryos, the same process behind natural identical twins. These offspring are identical to each other, but each still carries chromosomes from both parents, unlike a nuclear-transfer clone.

People may clone valuable pedigree animals like horses commercially. Attempts to clone human embryos as transplant donors remain controversial, with no settled answer.

Industrialization raised living standards but also created toxic industrial effluents. Heavy metals like lead from automobiles and chromium from tanneries now harm human health.

Bioremediation uses living organisms to remove or degrade these pollutants; algae, for instance, reduce heavy-metal pollution by bioabsorption. Biologists also list and protect endangered species before they go extinct.

In Pakistan, rivers and canals are heavily polluted by city sewage and industrial waste, and fish populations have declined the most. Automobile exhaust adds lead to city air, so the book calls for lead-free petrol.