Cell Division (Lecture 1)

Question 1

What is cell division?

Answer 1

The process by which cells make more cells

Question 2

Why does cell division occur?

Answer 2

– Growth – Cell replacement – Healing – Reproduction

Question 3

Cell division occurs by…

Answer 3

1. Mitosis (eg, hair stem cells) 2. Meiosis (germ or sex cells)

Question 4

If a stem cell divides once a day for 75 years how many times would it have divided without making a mistake?

Answer 4

Over 27,000

Question 5

What are the main stages of the cell cycle?

Answer 5

1. G1 phase 2. S phase 3. G2 phase 4. M phase 5. G0 phase

Question 6

What happens in the G1 phase (gap 1)?

Answer 6

Growth, cellular metabolism

Question 7

What happens in S phase (Synthesis)?

Answer 7

DNA replication (chromosome duplication)

Question 8

What happens in G2 phase (Gap 2)?

Answer 8

Preparation for mitosis

Question 9

What happens in M Phase (mitosis)?

Answer 9

Chromosomal separation and cytokinesis

Question 10

Which parts of the cell cycle are involved in interphase?

Answer 10

1. G1 phase 2. S phase 3. G2 phase 4. G0 phase

Question 11

Interphase is the time between…

Answer 11

Successive mitoses G1 + S + G2

Question 12

Cells exit the cell cycle from G1 and enter a state called… and why?

Answer 12

G0, Cells that are not actively cycling may exit

Question 13

Cells that enter the G0 state are said to be…

Answer 13

Quiescent

Question 14

What would be considered quiescent with respect to the cell cycle?

Answer 14

A neutron with its axon and dendrites would be quiescent with respect to the cell cycle. It will not re-enter the cell cycle

Question 15

What are homologous chromosomes?

Answer 15

Homologous chromosomes are two pieces of DNA within a diploid organism which carry the same genes, one from each parental source

Question 16

What is a centromere?

Answer 16

The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids

Question 17

After two homologous chromosomes undergo S phase what happens?

Answer 17

Each chromosome duplicates creating sister chromatids attached to one centromere

Question 18

What are sister chromatids?

Answer 18

A sister chromatid refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined together by a common centromere

Question 19

What events occur in Prophase?

Answer 19

Chromosomes condense. Centrosomes radiate microtubules and migrate to opposite poles

Question 20

What are chromatin fibres?

Answer 20

Chromatin is composed of DNA and histones that are packaged into thin, stringy fibers

Question 21

What is a nuclear envelope?

Answer 21

The double-layered membrane enclosing the nucleus of a eukaryotic cell. The nuclear envelope has pores that allow the passage of materials into and out of the nucleus. Also called nuclear membrane.

Question 22

What events occur in Prometaphase?

Answer 22

Microtubules of the mitotic spindle attach to chromosomes, nuclear envelope starts to break down

Question 23

What are kinetochores?

Answer 23

A complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach

Question 24

What events occur in Metaphase?

Answer 24

Chromosomes align in center of cell

Question 25

What events occur in Anaphase?

Answer 25

Sister chromatids (which become individual chromosomes when the centromere splits) separate and travel to opposite poles

Question 26

What events occur in Telophase?

Answer 26

Nuclear envelope re-forms and chromosomes decondense

Question 27

What are ploidy levels?

Answer 27

The number of complete sets of chromosomes in a cell

Question 28

What is a cell with a complete set of chromosomes?

Answer 28

Haploid

Question 29

Sperm cell or an egg cell would be an example of what cell?

Answer 29

Haploid cell

Question 30

What would a diploid cell have?

Answer 30

A diploid cell would have two complete sets of chromosomes. One copy from the mother and one copy from the father

Question 31

What are examples of diploid cells?

Answer 31

Example of a diploid cell would be a somatic cell, such as a leaf cell or a skin cell or a stem cell in your colon

Question 32

Explain haploid (n) vs diploid (2n)

Answer 32

When one unique chromosome from Dad’s germ cell (haploid cell (n)) comes together with 1 unique chromosome from Mom’s germ cell (haploid (n)) it creates one homolog (homologous chromosomes) which are now diploid cells (2n). 2 unique chromosomes (2n).

Question 33

What happens to diploid somatic cells after s phase?

Answer 33

Still considered a diploid cell, even though there are 4 complete sets of chromosomes. This is a short and transient phase. Note that the amount of DNA has doubled.

Question 34

What events occur in cytokinesis (animal)?

Answer 34

Cytokinesis divides the cytoplasm of a parental cell into two genetically identical daughter cells

Question 35

What types of cells does Mitosis occur in?

Answer 35

Stem cells

Question 36

Amount of ______ changes, but NOT the ________ level in Mitosis

Answer 36

Amount of DNA changes, but NOT the ploidy level in Mitosis