A long, threadlike structure that carries the bearer's genetic code (DNA), among other things. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes, the X (female) and less complex Y (male). Offspring acquire half their chromosomes from the biological mother and half from the biological father. Each chromosome is shaped like an X, with a dot in the center (the centromere) and arms reaching out to the ends (the irreplaceable telomeres that keep chromosomes from sticking together accidentally; their gradual shortening from replication after replication during cell division sets the biological limit to a life). See Gene, DNA.