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.
The sperm cell and the egg cell that come together to form the zygote each contain half the normal amount of DNA. There are 46 chromosomes in a typical human cell. The sperm and the egg each contain only 23 - one copy of chromosomes 1 through 22 plus an X or a Y. Egg cells can only contain an X but the sperm can contain an X or a Y. East Haven High School in CT (10th grade student)