What is the difference between autosomes and sex chromosomes? What determines the biological (genetic) sex of a baby human? a) Autosomes are chromosomes that determine an individual's sex, while sex chromosomes are involved in other genetic traits. The biological sex of a baby human is determined by the presence of either an X or Y chromosome. b) Autosomes are involved in determining an individual's sex, while sex chromosomes are responsible for other genetic traits. The biological sex of a baby human is determined by the combination of alleles on autosomes. c) Autosomes are responsible for other genetic traits, while sex chromosomes determine an individual's sex. The biological sex of a baby human is determined by the presence of two X chromosomes. d) Autosomes and sex chromosomes are both involved in determining an individual's sex. The biological sex of a baby human is determined by the presence of an X chromosome paired with either another X or a Y chromosome.