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NEL Cell Division 575

Comparing Mitosis and Meiosis

Single-celled eukaryotic species undergo asexual reproduction by mitosis, followed by

cytokinesis. In multicellular eukaryotic species, somatic cells undergo these same processes

in order to grow and repair tissue. In contrast, meiosis occurs only in the sex cells of

multicellular eukaryotic species, in order to produce the gametes needed for sexual

reproduction.

The most significant difference between mitosis and meiosis is the end result (Figure 6).

Mitosis results in two daughter cells that are identical to each other. The daughter cells

have the same genetic information and carry the same number of chromosomes as the

Section17. 3

Practice

1. Define meiosis. Describe the main stages in the process. Sketch the sequence of
   stages to help you in your description. Label your diagrams appropriately.
   2.How are haploid cells different from diploid cells in humans?
   3.What is a tetrad?
   4.What are homologous chromosomes?
   5.Do homologous chromosomes have the same number of genes? Explain.
   6.Do homologous chromosomes have identical genes? Explain.

miniInvestigation Gamete Formation in Grasshoppers

Obtain prepared slides of grasshopper (Figure 5) testes and

identify cells undergoing meiosis. Make a few sample diagrams

of cells at various stages of cell division.

(a) Label the chromosomes.

(b) Are you able to count the chromosome number? Explain

why or why not.

(c) Explain and compare what happens in prophase,

metaphase, and anaphase of meiosis I and II.

(d) How do cells undergoing meiosis II differ from cells

undergoing meiosis I?

Figure 5

Figure 6

Comparison of mitosis and meiosis

in humans. Mitosis produces two

diploid cells from one diploid cell.

Meiosis produces four haploid cells

from one diploid cell.

meiosis

diploid chromosome

number

haploid

chromosome

number

first meiotic

division

second meiotic

division

46

23 23

23 23 23 23

mitosis

46 46

46