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.
Body cells have pairs of chromosomes while sex cells have only single sets of chromosomes. The human body cells have 22 pairs of autosomes and 1 pair of sex chromosomes for a total of 23 pairs or 46 chromosomes. But sex cells (sperm or ovum, known as gametes or diploid cells) contain only 23 chromosomes (unpaired), when they meet (forming a Zygote), the 23 from each male and female gamete form a cell containing 46 chromosomes to make a Haploid cell. Normal body cells (known as a haploid cells) contain 46 chromosomes (or 23 pairs of chromosomes).