Chapter 9- Sexual Reproduction And Meiosis

Question 1

Life cycle of sexually reproducing organisms

Answer 1

Two types of cell division interact (mitosis and meiosis)

Zygotes become adults through mitosis

Mature adults produce sex cells by meiosis

Sex cells combine to fertilize and become zygotes

Question 2

Basic principles of meiosis

Answer 2

Occurs only in the reproductive organs (germ cells)

Diploid and haploid cells

Gametes result (egg or sperm, haploid)

1:4 cell division- one diploid becomes 4 non-identical haploid cells

Question 3

Diploid

Answer 3

Normal chromosome numbers in an organism

2n-> 46

Question 4

Haploid

Answer 4

Half the normal chromosome number

N-> 23

Question 5

Role and function of meiosis

Answer 5

Only in sexually reproductive organisms

Produces haploid gametes

Ensures offspring receive a dell set and correct # of chromosomes (46 or 23 pair homologous)

Introduces genetic variability

Question 6

Meiotic cell division

Answer 6

More complicated than mitosis

Basic cell cycle is the same

Cell division phase is now meiosis (2 divisions, M1 and M2)

Question 7

Meiosis I

Answer 7

Reductional division (reduces # of chr)

Chromosomes have already been replicated and occur in pairs (maternal/paternal)

Prophase I
metaphase I
Anaphase I
Telophase I
Cytokinesis
Interkinesis

Question 8

Prophase I

Answer 8

envelope disappears, centrosomes migrate, spindles appear and attach to centromeres

Synapsid: chromosomes find their homologous pair

Crossing over occurs- non-sisters exchange segments (genetic variability)

Question 9

Metaphase I

Answer 9

Homologous chromosomes line up on random sides in middle of cell

** independent assortment

Question 10

Anaphase I

Answer 10

Homologous chromosomes separate and move to poles

Question 11

Telophase I

Answer 11

Nuclear envelope reforms, centrosomes return, spindles disappear

Question 12

Cytokinesis

Answer 12

Cells cleave into 2 daughter cells

2 non-identical haploid daughter cells at end of Meiosis I

Question 13

Interkinesis

Answer 13

Cells grow slightly but no replication of DNA

Question 14

Meiosis II

Answer 14

Each cell divides again

Essentially same as mitosis PMAT + cytokinesis

In anaphase the sister chromatids separate and move to poles

4 non-identical haploid gametes at end of meiosis II

Question 15

Mitosis breakdown

Answer 15

Somatic cells

1:2 division

Diploid-> diploid

Asexual

2 identical daughter cells

Occurs all the time

Question 16

Meiosis breakdown

Answer 16

Germ cells

1:4 division

Diploid-> haploid

Sexual

To produce gametes

4 non-identical daughter cells

Less frequent until age of sexual maturity