In the cells with 45 chromosomes, the presence of 15 chromosomes in the size range of 6 to 12 plus X, and only two pairs in the 21, 22 range indicate an XO sex-chromosome constitution.

Males, on the other hand, carry only one X chromosome (XO) and produce some gametes with X chromosomes and some gametes with no sex chromosomes at all (Figure 5). Figure 6: Sex determination in birds.

Aphids are insects with a sex determination model based on the presence of two X chromosomes (XX) in females and a single X chromosome (XO) in males.

Chromosome Pattern of the Patient, Showing an XO Cell (45 Chromosomes) from the Same Culture as the Cell in Figure 3. Of the 217 leukocytes analyzed, 42 (19.4 per cent) had 45 chromosomes, and 170 ...