Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with many forms of cancer, and causes 90% of lung cancer.
Human diploid cells have 46 chromosomes and human haploid gametes (egg and sperm) have 23 chromosomes. Retroviruses that contain two copies of their RNA genome in each viral particle are also said to be diploid.
There are 46 chromosomes (23 pairs) in a human body cell with the exception of the sex cells. One of each pair is inherited from the mother's egg, the other from the father's sperm. When the sperm and egg unite in fertilization, they create a single cell, or zygote, with 46 chromosomes.omatic cells (body cells) are haploid cells. They have 23 pairs of chromosomes. Reproductive cells (gametes) have half the normal number i.e. 23. This is because two gametes (one male and one female) have to fuse hence, restoring the original number of 23 pairs.