Watch my introduction to Genetics video and make notes on it. Note that there is an important correction in the video:
CORRECTION: I would like to clarify that the gender identity " girl" or "boy" does not necessarily correspond to the genotypes XX and XY. Someone with female gametes and genotype XX can be: a trans man, a cis woman, a nonbinary person or an agender person. Also genotype XY can be: a trans woman, a cis man, a nonbinary person or an agender person. There is one section of the video where I refer to a "girl" as xx and a "boy as xy. This is incorrect.