Psychology Glossary. Genotype. The total set of genes contained within an organisms cells. Organisms contain some genes that are expressed (you can consider the expressed to mean that the gene is active or being used) and some that are not. Regardless, all the genes an organism has are considered the genotype.
Mars' closest approach to the Earth is called opposition, and occurs roughly every 780 days.
In theory, the closest the planets could come together would be when Mars is at its closest point to the Sun (perihelion) and Earth is at its farthest point (aphelion). In that case, the planets would be 33.9 million miles (54.6 million kilometers or 0.3646 AU) from each other.