Biology chapter 13 - Meiosis

Somatic cells are

diploid (2n) body cells

Gametes are

sex cells, haploid

Diploid cells are?

2n

haploid cell

A cell containing only one set of chromosomes (n).

Why does sexual reproduction require meiosis?

meiosis results in gametes, and sexual reproduction involves the fusion of a female and a male gamete. Meiosis reduces the number of chromosomes, resulting in four haploid gametes. When haploid gametes fuse during fertilization, the zygote has two sets of chromosomes.

sex chromosomes are?

X (for female) and Y (for male) chromosomes.

Karyotype is?

organized representation of the chromosomes within a cell

homologous chromosomes

Chromosomes that have the same sequence of genes and the same structure

Meiosis I phases

Prophase I, Metaphase I, Anaphase I, Telophase I

Prophase 1 (Meiosis I )

Chromosomes become visible; nuclear envelope breaks down; crossing-over occurs.

- 3 homologous pairs

-mitotic spindle creation

- homologous chromosomes pair up.

Metaphase I (Meiosis)

Homologous chromosomes separate, but are attached at the centromere

- lined up at the plate

-Independent assortment occures

Telophase I and Cytokinesis (Meiosis)

The cell divides into two new cells, and the nuclear membrane appears in each cell.

Meiosis II

the second phase of meiosis consisting of chromatids separating, along with the two diploid cells splitting in two

Prophase II in Metaphase II

-chromosomes are again condensed and visible

-new centriole form

Metaphase II

Chromosomes line up at the equator.

Anaphase II

Sister chromatids separate to opposite poles.

Telophase II and Cytokinesis

A nuclear envelope forms around each set of chromosomes. the cytoplasm divides. (Haploid cells) different from one another.

independent assortment

Independent segregation of genes during the formation of gametes

crossing over

-Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

-Produces recombinant chromosomes.

Anaphase I (Meiosis)

homologous chromosomes separate, pulled to opposite poles by centromeric spindle fibers

random fertilization

source of genetic variation caused by the unlimited number of possible sperm & egg combinations

In Meiosis II, ___ cells are divided into 4 ___ daughter cells

haploid; haploid