Biology Now, 2e

110 ■ CHAPTER 06 Cell Division

CELLS

Combination 1 Combination 2 Combination 3 Combination 4

Metaphase of

meiosis I

Metaphase of

meiosis II

Gametes

At the end of

meiosis II, sister

chromatids are

segregated into

separate

daughter cells.

Four possible combinations of chromosomes

in gametes generated by meiosis II.

Maternal

homologue

Paternal

homologue

Option A If we consider just two pairs of homologous Option B

chromosomes, there are two ways in which

they can be oriented relative to each other

after prophase I during metaphase I.

The maternal and

paternal homologues

of each pair are sorted

into two daughter cells

through anaphase I,

telophase I, and

cytokinesis.

Figure 6.10

The independent assortment of homologous chromosomes generates

chromosomal diversity among gametes

Only two pairs of homologous chromosomes are shown here, rather than the 23 homologous pairs in

human cells. Each gamete will receive either a maternal or a paternal homologue of each chromosome.

Only the resulting cells of metaphase I, metaphase II, and the resulting gametes of the process of

meiosis are depicted here.

Q1: During meiosis, does random assortment occur before or after crossing-over?

Q2: What would be the effect on genetic diversity if homologous chromosomes did not

randomly separate into the daughter cells during meiosis?

Q3: With two pairs of homologous chromosomes, four kinds of gametes can be produced. How

many kinds of gametes can be produced with three pairs of homologous chromosomes? What

does this suggest for the 23 homologous pairs of chromosomes in human cells?