Meiosis

Question 1

What do mitotic cells function in?

Answer 1

Growth, replacement of damaged or lost cells, and asexual reproduction.

Question 2

What is the involvement of meiosis in sexual reproduction?

Answer 2

The formation of gametes (eggs and sperm)

Question 3

What happens to the number of pairs of chromosomes in meiosis?

Answer 3

The number of pairs is reduced from 2 pairs to 1 pair (in the gametes).

Question 4

How many sets are received by the daughter cells in meiosis and mitosis?

Answer 4

In meiosis, 1 complete set is received by the gametes. In mitosis, every cell gets an exact copy of the complete genetic info (both sets).

Question 5

Why is meiosis necessary?

Answer 5

Because the number of pairs of chromosomes must be kept constant in the future generations. (otherwise there would be a doubling every generation)

Question 6

How is called the fusion of two gametes?

Answer 6

Fertilization

Question 7

What cell does the fusion of two gametes (haploid) produce?

Answer 7

A diploid zygote

Question 8

What alternates in life cycles for sexually reproducing organisms?

Answer 8

Haploid and diploid stages alternate. The length of each depends on the life cycles.

Question 9

What happens with diploid zygotes?

Answer 9

They undergo mitosis to give rise to all cells in the body.

Question 10

How are called the cells (2n) that are set aside for meiosis and what do they produce?

Answer 10

Germ-line cells and they prodduce gametes (n).

Question 11

Does the interphase vary before meiosis and mitosis?

Answer 11

No, it is the same. Chromosomes are copied in S phase, and there is a formation of spindle and chromosome shortening in the G2 phase.

Question 12

How many daughter cells are resultant after the 2 meiosis?

Answer 12

A total of 4 daughter cells.

Question 13

What are homologuous chromosomes?

Answer 13

Two chromosomes in a pair that contain the same linear sequence of genes. Each homologue was equally contributed by eeach parent

Ex:
Dad set: 1, 2, 3, 4,…, 23
Mom set: 1, 2, 3, 4,…,23

The #1s have the same genes and form a homologuous pair

Question 14

When does the cell become haploid?

Answer 14

The two daughter cells become haploid after telophase 1/interkinesis

Question 15

What are the phases of meiosis 1?

Answer 15

Prophase 1, metaphase 1, anaphase 1, telophase 1, and interkinesis.

Question 16

What happens in prophase 1?

Answer 16

Nuclear enveloppe disappears, nucleolus disappears, centrioles are at the opposite sides of the cell, spindle apparatus forms, homologues become closely associated in synapsis, and crossing over occurs.

Question 17

What happens in metaphase 1?

Answer 17

Microtubules from opposite poles attach to each homologue, not each sister chromatid. Homologues (tetrads) are aligned at the metaphase plate. The orientation of each homologue is random.

Question 18

How are homologues attached in meiosis?

Answer 18

They are attached with chiastama. The kinetochores fuse and the microtubules can only attach to one side of each centromere.

Question 19

What happens in anaphase 1?

Answer 19

The homologues are separated from each other and the sister chromatids remain attached at the centromere.

Question 20

What happens in telophase 1?

Answer 20

The nuclear enveloppe may form around each set of chromosomes. Each nucleus is now haploid. Both sister chromatids are now not identical because of crossing over.

Question 21

What happens in interkinesis?

Answer 21

The cytoplasm of the cell divides into 2. However, no cell cycle occurs after that (DNA replication, etc). The cells rest prior to second set of division.

Question 22

What happens in prophase 2?

Answer 22

Nuclear enveloppe disappears if it reformed. New spindle forms.

Question 23

What happens in metaphase 2?

Answer 23

Spindle fibers from opposite poles bind to kinetochores of each non-identical sister chromatid. They align on the metaphase plate.

Question 24

What happens in anaphase 2?

Answer 24

Spindles contract and the cohesion complex joining the centromeres break and chromatids separate. Non identical sister chromatids are moved to opposite poles.

Question 25

What happens in telophase 2?

Answer 25

Chromosomes are drawn to opposite ends of the cell and nuclear enveloppe surrounds the chromosomes.

Question 26

What happens in cytokinesis?

Answer 26

Each daughter cell divides. Each daughter cell has 1 set of chromosomes, not 2. Will transform into gametes for animals. May also divide by mitosis (for plants, fungi or protists).

Question 27

Name a similarirty between mitosis and meiosis

Answer 27

The chromosomes only duplicate once (interphase).

Question 28

Name a difference between mitosis and mitosis

Answer 28

Mitosis: one division of the nucleus… 2 diploid daughter cells.
Meiosis: 2 nuclear and cytoplasmic divisions… 4 haploid cells.

Question 29

Name some unique features to meiosis

Answer 29

Pairing of homologuous pairs to form tetrads.
Crossing over between homologuous chromatids.

Tetrads are aligned at the metaphase plate.

In anaphase, the pairs separate but the sister chromatids stay together.

Question 30

Why does meiosis bring variability in the offspring?

Answer 30

Because there may be reschuffling of genes or mutations.

Question 31

Do the offspring vary (in meiosis)?

Answer 31

Yes, they vary from their parents and from one another.

Question 32

What causes reshuffling of genes?

Answer 32

Independent assortment of chromosomes pairs during metaphase 1 leads to many different possibilities.
Random fertilization of eggs by sperm greatly increases this variation.

Question 33

How does crossing over impact the 4 daughter cells?

Answer 33

It results in gametes of 4 different genetic types.

Question 34

What are alleles?

Answer 34

Different versions of a gene.

Question 35

Crossing over is a form of _______?

Answer 35

Genetic recombination.