Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 25

The Gonads: Development & Function of the Reproductive System 393

FIGURE 25–1
Basis of genetic sex determination.
In the two-stage meiotic division in the female, only one cell survives as the mature
ovum. In the male, the meiotic division results in the formation of four sperms, two containing the X and two the Y chromosome. Fertilization thus
produces a male zygote with 22 pairs of autosomes plus an X and a Y or a female zygote with 22 pairs of autosomes and two X chromosomes. Note
that for clarity, this figure and Figures 25–6 and 25–7 differ from the current international nomenclature for karyotypes, which lists the total num-
ber of chromosomes followed by the sex chromosome pattern. Thus, XO is 45, X; XY is 46, XY; XXY is 47, XXY, and so on.

FIGURE 25–2
Karyotype of chromosomes from a normal male.
The chromosomes have been stained with Giemsa’s stain, which produc-
es a characteristic banding pattern.
(Reproduced with permission, from Lingappa VJ, Farey K:
Physiological Medicine.
McGraw-Hill, 2000.)

FIGURE 25–3
Left: Barr body (arrows) in the epidermal spinous cell layer. Right: Nuclear appendage (“drumstick”) identified by
arrow in white blood cells.
(Reproduced with permission from Grumbach MM, Barr ML: Cytologic tests of chromosomal sex in relation to sex anomalies in man. Recent
Prog Horm Res 1958;14:255.)

44

XY

Meiosis Fertilization

44

XX

Zygotes

44

XY

44

XX

44

XX

22

Y

22

X

22

X

22

X

22

X

22

X

22Y

22Y

22X

22X 22X

22X

Mature

sperms

Mature

ova

Immature

ova

Primary

spermatocyte

Meiosis

22X

(First

polar body)

22X

(Second

polar body)

1

6

13

19 20 21 22

14 15 16 17 18

789101112

23 45

XY

aa bb aa bb