How a change in DNA can lead to a change in phenotype. With an example

Variation within genes leads to different genotypes , which can be seen by the individuals having different phenotypes . For example, the dogs above all have different fur colours and fur lengths. Genetic and environmental variation combine together to produce these different phenotypes.

The mass of an atom comes from the protons and neutrons that are found in the nucleus. The number of protons is the atomic number of an element. To find the number of neutrons, subtract the atomic number from the mass of an atom. So, if an atom is missing a neutron or has an extra neutron, the atom is called an isotope. An atom is still the same element if it is missing an electron. That is also true for isotopes. They are the same element but their number of neutron differs.