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578 Chapter 17 NEL

Development of Male and Female Gametes

The formation of sex cells during meiosis is referred to as gametogenesis. Although

human male and female gametes both follow the general process of meiosis, some dif-

ferences do exist. The cytoplasm of the female gametes does not divide equally after

each nuclear division. As shown in Figure 9, one of the daughter cells, called the ootid,

receives most of the cytoplasm. The other cells, the polar bodies, die, and the nutrients

are absorbed by the body of the organism. Only one ovum (egg cell) is produced from

meiosis. In contrast, with sperm cells, there is an equal division of cytoplasm. Sperm

cells have much less cytoplasm than egg cells.Sperm cells are specially designed for

movement: they are streamlined and cannot carry excess weight. Egg cells use the nutri-

Practice

7. Copy and complete Table 1. Compare the chromosome number in the organisms
   before, during, and as a result of meiosis. Indicate whether the chromosome number
   is haploid or diploid.
   Table 1 Chromosome Number in Cells of Four Organisms

Human Cat Shrimp Bean

Before meiosis

chromosome number 46???

(haploid or diploid?)

number of pairs of 23? 127?

homologous chromosomes

After meiosis I

chromosome number 23 19??

(haploid or diploid?)

After meiosis II

chromosome number 23?? 11

(haploid or diploid?)

number of pairs of 0???

homologous chromosomes

gametogenesisthe formation of
gametes (sex cells) in animals

ootidan unfertilized ovum

Spermatogenesis

four sperm cells

ootid

polar bodies

first polar body

spermatocyte

chromosome

number

oocyte

Oogenesis

First meiotic

division

Second

meiotic

division

46

23 23 23 23

46 4646

(^2323232323232323)
2323 2323 2323 2323
Figure 9
Generalized diagram of sperm and
egg cell formation in humans