Coal seams are far deep underground to be considered for opencast minings. These coal seams require underground mining. Since it is too deep underground, it can be used for mapping and correlation of sedimentary rocks or as a key bed.
A gamete is a haploid cell, a cell with only one pair of chromosomes. Say the skin cell of a human has 46 chromosomes (2 pairs), a gamete would have 23 chromosomes (1 pair) because gametes are sex cells. When a sex cell (Egg and sperm) come together, they together will create a dipole cell (46 chromosomes, 2 pairs).
