Chapter 11

Question 1

Diploid cells

Answer 1

2n Somatic cells. 2 sets of chromosomes

Question 2

Haploid cells

Answer 2

n. Gametes have 1 set of chromosomes
Inheritance - 1 set of chromosomes from each parent

Question 3

Zygote

Answer 3

undergoes mitosis to produce diploid cells. zygote into fetus into child into adult

Question 4

Meiosis

Answer 4

Two rounds of cells division. Start with one cell and end with 4 cells with genetic variation.
Meiosis I (reduction division, separate chromosomes) and Meiosis II (separate chromatids) NO S phase
PMAT - Prophase I, Metaphase I, Anaphase I, Telophase I. Prophase II, Metaphase II, Telophase II.

Question 5

Synapsis

Answer 5

(crossing over) during early prophase I homologous chromosomes become closely associated and eventually swap DNA.
Tetrads

Question 6

Prophase I

Answer 6

Chromosomes condense, nuclear envelope disappears, spindle fibers form from centrosomes. Each chromosome composed of 2 sister chromatids. Homologous chromosomes become paired (synapse tetrads). Genetic variation from crossing over, random exchange of DNA between non-sister chromatids of homologous pairs of chromosomes.

Question 7

Crossing Over

Answer 7

Occurs between non-sister chromatids to allow maternal and paternal homologues to exchange chromosomal material. Alleles form on separate homologues.

Question 8

Chiasmata

Answer 8

Site of crossing over. Contact maintained until anaphase I

Question 9

Metaphase I

Answer 9

Not single file line, homologous pairs of chromosomes are aligned at metaphase plate side by side. Orientation random (independent assortment). Microtubules attach from opposite poles to each homologue, not each sister chromatid

Question 10

Anaphase I

Answer 10

Separate homologous pairs. Chiasmata break, sister or non-sister chromatids remain attached to each other at their centromeres. Each pole has complete haploid set of chromosomes consisting of one member of each homologous pair.

Question 11

Telophase I

Answer 11

Nuclear envelope re-forms around each daughter nucleus. Cytokinesis may or may not occur after telophase I depending on species.

Question 12

Prophase II

Answer 12

Follows a brief or no interphase, no S phase. Chromosomes move toward metaphase plate.

Question 13

Metaphase II

Answer 13

Chromosomes align on metaphase plate, kinetochore microtubules from opposite poles attach to kinetochores.

Question 14

Anaphase II

Answer 14

Microtubules shorten and sister chromatids break and are pulled to opposite poles

Question 15

Telophase II

Answer 15

Nuclear membrane reforms around four different clusters of chromosomes. After cytokinesis 4 haploid cells

Question 16

Final result of meiosis

Answer 16

Four haploid cells that are unique. Animals 4 spermtogenesis and 4 oogenesis (1 egg, usable and 3 polar bodies, unusable).
Some plants, fungi and protists divide haploid by mitosis

Question 17

Errors in meiosis

Answer 17

Nondisjunction-failure of chromosomes to move to opposite poles during either meiotic divisions
Aneuploid gametes-Gametes with missing or extra chromosomes