3.21 understand that the sex of a person is controntrolled by one pair of chrmosomes, XX in a female and XY in a male

Firstly, it is important to understand that there are 23 pairs of chromosomes in each human cell, resulting is 46 individual chromosomes. (NOTE: there are only 23 chromosomes in sex cells, this is known as haploid). The 23rd pair is the one that determines whether you are male or female. Every male has 'XY' as his 23rd pair and every female has 'XX' as their 23rd pair. The female can only give X alleles, whilst the male can give X or Y alleles. This results in a combination of 2 XX genotypes and 2 XY genotypes, meaning there is a 50% chance of being male and a 50% chance of being female. This diagram may help for understanding...


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