Meiosis

Question 1

What is a germ cell?

Answer 1

Gamete

Question 2

How many chromosomes are left after Meiosis?

Answer 2

23

Question 3

How many daughter cells result from Mitosis and Meiosis? What is their n?

Answer 3

Meiosis: 4 haploid (n) daughter cells
Mitosis: 2 diploid (2n) daughter cells

Question 4

What happens in Prophase I of Meiosis

Answer 4

(condensation)

• The nucleoli dissolve
• The chromatin condenses into chromosomes
• The MTOCs move to opposite sides of the cell and start sending out microtubules
• The nuclear envelope dissolves
• The chromosomes start to line up randomly as homologous pairs
• The homologous pairs form close associations called a chiasmata
• Crossing over between homologues of chromosomes occurs at the chiasmata

Question 5

What happens during Metaphase I of Meiosis?

Answer 5

(alignment)

• Chromosomes line up at the center of the cell.
• Microtubules attach to one kinetechore on each of the centromere’s of the homologous pairs from opposite poles.

Question 6

What happens during Anaphase I of Meiosis?

Answer 6

(separation)

- Homologous chromosomes are separated as the MTOCs’ microtubules shorten.

Question 7

What happens during Telophase I of Meiosis?

Answer 7

(restoration)

• The chromosomes have reached their respective poles and a nuclear envelope begins to form around them.
• Cytokinesis occurs forming a cleavage furrow or cell plate in most organisms.
• The cells consist of 23 chromosome and 46 chromatids, and are haploid.

Question 8

What happens during Prophase II of Meiosis?

Answer 8

(condensation)

• The nuclear envelope dissolves
• The spindle begins to develop and move to opposite sides of the cell
• There is no crossing over that occurs

Question 9

What happens during Metaphase II of Meiosis?

Answer 9

(alignment)

• The chromosomes align singly on the metaphase plate (not in homologous pairs)
• Microtubules connect to the kinetechore on each side of the centromere and pull until the chromatids separate.
• This is analogous to Mitosis, but with half the number of chromosomes.

Question 10

What happens during Anaphase II of Meiosis?

Answer 10

(separation)

• Microtubules shorten on the chromosome end, to pull the chromosomes to opposite sides of the poles.
• Microtubules not attached to chromosomes push on each other to help form poles.
• Similar to Mitosis, except for half the chromosomes

Question 11

What happens during Telophase II of Meiosis?

Answer 11

(restoration)

• The nuclear envelope reappears at each pole
• cytokinesis begins
• The result is four daughter cells with 23 single chromatid chromosomes.

Question 12

synapsis

Answer 12

The process in which homologous pairs of chromosomes pair up during Meiosis

Question 13

chiasmata

Answer 13

The close associations of non sister chromatids during Meiosis where crossing over can occur

Question 14

linkage

Answer 14

The tendency of genes on the same chromosome to stay together in the same gamete.

The greater the distance between two genes on a chromosome, the more likely crossing over and recombination is to occur between them. The close they are together, the less likely crossing over occurs

Question 15

synaptonemal complex

Answer 15

a protein structure that maintains the synapsis process in a fixed state until crossing over occurs.

Question 16

syngamy

Answer 16

Another name for fertilization

Question 17

Where is sperm made?

Answer 17

• in the seminiferous tubules of the testes
• LH (leutinizing hormone) and FSH (follicle stimulating hormone work together to stimulate spermatogenesis
• It’s being made continuously
• Meiosis yields four sperm cells

Question 18

What are the names of sperm cells during Meiosis?

Answer 18

Spermatogonium - Starting diploid cell that undergoes mitosis to create a primary spermatocyte (diploid cell)

Primary spermatocyte (diploid) - undergoes Meiosis I to form two haploid secondary spermatocytes with 46 chromatids

Secondary spermatocytes (haploid) - undergoes Meiosis II to form spermatids with 23 chromosomes and 23 chromatids

spermatids - sperm gametes

Question 19

spermatogonium

Answer 19

Starting diploid cell that undergoes mitosis to create a primary spermatocyte (diploid cell)

Question 20

Primary Spermatocyte

Answer 20

(diploid) undergoes Meiosis I to form two haploid secondary spermatocytes with 46 chromatids

Question 21

Secondary spermatocytes

Answer 21

(haploid) undergoes Meiosis II to form spermatids with 23 chromosomes and 23 chromatids

Question 22

spermatid

Answer 22

(haploid) immature sperm gamete that will develop without further cell division

Question 23

acrosome

Answer 23

Head of the sperm.

Contains hyaluronidase enzymes which can break down the zona pellucida (outer membrane of ova), allowing for syngamy (fertilization)

Question 24

Hyaluronidase

Answer 24

Enzyme that can break down the zona pellucida (outer membrane of the ova)

Question 25

What are the names of egg cells during development?

Answer 25

oogonia (diploid)

primary oocyte (diploid)

secondary oocyte (haploid)

oveum (egg cell) (haploid)

Question 26

Where are eggs made?

Answer 26

• In the ovaries
• Early cells stop meiosis and stay in Prophase I until puberty
• One follicle will mature each month, giving rise to a cell that has the potential to be fertilized
• The secondary oocyte is what gets fertilized. It resumes meiosis at that time and then allows syngamy to occur.

Question 27

What type of egg cell is actually fertilized?

Answer 27

secondary oocyte

Question 28

What is capacitation?

Answer 28

It is the penultimate step in sperm maturation.

It occurs after eaculation and enzymes in the uterus help the sperm swim faster and penetrate the egg (secondary oocyte)