Mitosis & Meiosis

Question 1

What is mitosis?

Answer 1

Typical cell growth

Results in daughter cells having the same number and kind of cells as the parent cell

Occurs in somatic cells

Question 2

What is meiosis?

Answer 2

Division and duplication of reproductive cells

There are two nuclear divisions that occur and four haploid cells are produced

Question 3

What is the cell cycle?

Answer 3

2 stages: interphase and actual cell division (mitosis)

Cells spend most of their life in interphase (growing and DNA replication)

Question 4

What are the stages of interphase?

Answer 4

G1: rapid cell growth

S: Synthesis - duplication of chromosomes

G2: more growth, getting ready for another cell division

Question 5

What are the four phases of mitosis?

Answer 5

Prophase (prepare)

Metaphase (middle)

Anaphase (apart)

Telophase (two)

Question 6

What happens in prophase?

Answer 6

Chromosomes become visible under a microscope as they shorten and thicken

Nuclear membrane breaks down

Centrioles move to opposite pole creating spindle fibres between them

Question 7

What are centrioles?

Answer 7

Small protein body found in the cytoplasm that migrate to opposite poles

Question 8

What are spindle fibres?

Answer 8

Protein structure that attaches to centrioles and guides chromosomes during cell division

Question 9

What happens in metaphase?

Answer 9

Chromosomes composed of sister chromatids move to the center of cell (equatorial plate)

Chromosomes appear as dark, thick, filamentous structures and become intertwined

Question 10

What happens in anaphase?

Answer 10

The centromere splits apart and the chromatids move to opposite poles along the spindle fibres

If mitosis proceeds correctly, the same number and type of chromosomes will be found at each pole

Question 11

What happens in telophase?

Answer 11

The chromosomes reach the poles

A new nuclear envelope forms around each ear of separated chromosomes

Mitosis is complete, but cell division is not yet complete

Question 12

What is cytokinesis?

Answer 12

Divides the cytoplasm and its organelles roughly equally into two daughter cells in somatic cells

Question 13

What two cells can reproduce endlessly?

Answer 13

Sperm cells

Cancer cells

Question 14

What is the diploid number?

Answer 14

The diploid chromosome number is 46 in humans

Refers to the entire amount of chromosomes present in a human cell

Can be represented as 2n

Question 15

What is the haploid number?

Answer 15

The haploid chromosome number is 23 in humans

Humans have 23 pairs of chromosomes

Can be represented by n

Question 16

What happens in prophase 1 in meiosis 1?

Answer 16

Chromosomes condense and become visible, centrioles move toward the poles, and nuclear membrane begins to dissolve

Homologous chromosomes pair up, forming tetrads

Each tetras is comprised of four chromatids

Question 17

What is the process of crossing over?

Answer 17

Occurs in prophase 1 and metaphase 1 of meiosis 1

Homologous pairs will swap genetic material

Crossing over serves to increase genetic diversity by creating four unique chromatids

Question 18

What happens in metaphase 1 in meiosis 1?

Answer 18

Homologous chromosomes attach to spindle fibres and line up in the middle (equatorial plate)

Question 19

What happens in anaphase 1 in meiosis 1?

Answer 19

The homologous chromosomes separate

Question 20

What happens in telophase 1 in meiosis 1?

Answer 20

Nucleus completes division, the chromosomes are still composed of sister chromatids

Question 21

What happens in meiosis 2?

Answer 21

Prophase 2, metaphase 2, anaphase 2, and telophase 2, repeats the same steps but with half as much genetic material

There is no replication of chromosomes prior to meiosis 2

Question 22

What happens in cytokinesis 2 in meiosis 2?

Answer 22

The final step of meiosis where each cell splits into two daughter cells

A total of four gametes, each with half the number of chromosomes is formed

Question 23

What is nondisjunction?

Answer 23

When two homologous chromosomes fail to separate

One of the daughter cells will have too many chromosomes, the other too few

Question 24

What is a trisomy?

Answer 24

If the gamete with 24 joins a normal gamete with 23, the resulting individual will have 47 rather than 46 chromosomes

Question 25

What is a monosomy?

Answer 25

If the gamete with 22 joins a normal gamete with 23, the resulting individual will have 45 chromosomes rather than 46

Question 26

What causes Down syndrome?

Answer 26

Trisomy 21

Three copies of chromosome 21

Question 27

What causes Turner syndrome?

Answer 27

Produces females with a single X chromosome

Question 28

What causes Klinefelter Syndrome?

Answer 28

Inherits two X chromosomes and one Y