Human spaceflight (also mentioned as crewed spaceflight or manned spaceflight) is spaceflight with a crew or passengers aboard a spacecraft. Spacecraft carrying people could also be operated directly, by the human crew, or it's going to be either remotely operated from ground stations on Earth or be autonomous, ready to carry out a specific mission with no human involvement. These are usually treated separately because of the nuclear genome, and therefore the mitochondrial genome. Human genomes include both protein-coding DNA genes and noncoding DNA. Haploid human genomes, which are contained in germ cells (the egg and sperm gamete cells created within the meiosis phase of amphimixis before fertilization creates a zygote) consist of three billion DNA base pairs, while diploid genomes (found in somatic cells) have twice the DNA content.