Meiosis

Question 1

What does sexual reproduction allow?

Answer 1

Genetic Variety.

Question 2

What are gametes?

Answer 2

Gametes are sex cells;

They undergo meiosis to:

• Create genetic variability and diversity
• Reduce chromosomes from diploid to haploid
• Daughter cells are genetically unique to the parent cell

Question 3

What are somatic cells?

Answer 3

Somatic cells are body cells;

They undergo mitosis to:

• Grow
• Repair damaged cells
• Replace old or dead cells
• Daughter cells are genetically identical to the parent cell

Question 4

What does meiosis prevent?

Answer 4

Meiosis prevents the “doubling” of genetic information.

Question 5

What do fused gametes form after fertilization?

Answer 5

A zygote.

Question 6

How many chromosomes does each gamete contain?

Answer 6

23 Chromosomes.

Question 7

How many chromosomes does each zygote contain?

Answer 7

46 Chromosomes.

Question 8

What is the human life cycle?

Answer 8

Zygote -> Embryo -> Fetus -> Human

Question 9

How many phases does the gamete production process have?

Answer 9

3 Phases:

• Interphase
• 2 Rounds of meiosis

Question 10

What are Homologous Chromosomes?

Answer 10

Two matching chromosomes with the
same size, same types of genes in the same locations.

Question 11

What are Sister Chromatids?

Answer 11

Two identical copies of the same chromosome formed by DNA replication, attached at the centromere.

Question 12

What happens in Interphase for meiosis?

Answer 12

The DNA replicates itself.

• Before replication, there are 46 chromosomes (46 chromatids)
• After replication, there are still 46 chromosomes (92 chromatids)

Question 12

What is a tetrad?

Answer 12

Two pairs of Homologous Chromosomes.

Question 13

What is the purpose of Meiosis 1?

Answer 13

The purpose of meiosis 1 is to reduce the amount of chromosomes by half, also known as the reduction phase.

Question 14

What happens in Prophase 1? (Meiosis)

Answer 14

• Centrioles move to opposite poles
• Spindle fibres form from centrioles
• Chromatin has condensed to form chromosomes
• The nuclear membrane breaks down
• Genetic recombination occurs between each tetrad; also known as crossing over

Question 15

What happens in Metaphase 1? (Meiosis)

Answer 15

• Chromosomes line up along equation in pairs (tetrads)
• Line up with their Homologous pair

Question 16

What happens in Anaphase 1? (Meiosis)

Answer 16

• Chromosome pairs are separated and pulled away to opposite ends by shortening of spindle fibres
• The sister chromatids do NOT separate (different than mitosis)
• Only the tetrad is broken up, but sister chromatids are still attached at the centromere

Question 17

What happens in Telophase 1? (Meiosis)

Answer 17

• Nuclear membrane reforms (2 of them now)
• Spindle fibres retract
• Cleavage Furrow (starts to pinch)

Question 18

What happens in Cytokinesis during Meiosis 1?

Answer 18

• Cytokinesis occurs forming two genetically different daughter cells
• Each daughter cell has half (haploid – n) the number of chromosomes as the parent cell (diploid -2n)

Before MEIOSIS I – 46 CHROMOSOMES (92 CHROMATIDS)

After MEIOSIS I – 23 CHROMOSOMES (46 CHROMATIDS)

Question 19

What is the purpose of Meiosis 2?

Answer 19

Meiosis is the equational division.

• Similar to mitosis, but no duplication of chromosomes during a very short interphase (no G1 or S phase)
• End result – four haploid cells

Question 20

What happens in Prophase 2? (Meiosis)

Answer 20

• Nuclear membrane begins to break down
• Spindle fibers begin to form
• Centrioles begin to move to poles

Question 21

What happens in Metaphase 2? (Meiosis)

Answer 21

• Chromosome pairs align along equator of cell.
• Spindle fibers attach to centromeres of chromatids
  (chromatids no longer identical because of crossing over)

Question 22

What happens in Anaphase 2? (Meiosis)

Answer 22

Spindle fibers pull chromatids apart

Question 23

What happens in Telophase 2? (Meiosis)

Answer 23

• Nuclear membrane re-assembles
• Chromosomes uncoil
• Spindles disappear

Question 24

What is the purpose of Cytokinesis in Meiosis 2?

Answer 24

• Four genetically different daughter cells form
• Each daughter cell still has half the number of chromosomes as the diploid cell (haploid-n)

Before MEIOSIS II – 23 CHROMOSOMES (46 CHROMATIDS)

After MEIOSIS II – 23 CHROMOSOMES (23 CHROMATIDS)