Cellular division

Question 1

Mitosis

Answer 1

division of the nucleus

Question 2

Cytokinesis

Answer 2

division of the cytoplasm
- creates two genetically identical daughter cells

Question 3

Mitosis phases

Answer 3

Prophase
Metaphase
Anaphase
Telophase
- Cytokinesis

Question 4

Chromatin

Answer 4

Chromosomes plus proteins
- RELAXED AND NON DIVIDING

Question 5

Chromosomes

Answer 5

Contain genetic information
- CONDENSED/DIVIDING

Question 6

Most organisms have pairs of chromosomes called what?

Answer 6

homologous chromosomes (aka homologues)
1 maternal
1 paternal

Question 7

How many chromosomes in G1?

Answer 7

One copy of each homologous chromosome
- monad chromosome (one DNA molecule/chromosome)

Question 8

How many chromosomes after S phase?

Answer 8

Dyad chromosomes
- two sister chromatids held together by a centromere
- TWO DNA molecules but still ONE CHROMOSOME

Question 9

Centromere

Answer 9

constriction in the chromosome
- site of microtubule attachment during mitosis

Question 10

DNA replication during S phase produces sister chromatids

Answer 10

One mitotic chromosome consists of TWO sister chromatids

Question 11

Human cells

Answer 11

N= 23 chromosomes
2N= 46 chromosomes

Question 12

After DNA replication

Answer 12

2N=46 chromosomes, so 46 times 2 chromatids per chromosome= 92 chromatids

Question 13

What holds replicated chromosomes/sister chromatids together until mitosis?

Answer 13

Cohesin

Question 14

Cohesin

Answer 14

• assembled during S phase
• forms a ring
• by metaphase of mitosis, sister chromatids are only held together by cohesin at centromere

Question 15

What forms the classic X-shaped metaphase chromosomes?

Answer 15

Centromeres

Question 16

What assembles on centromeres?

Answer 16

Kinetochore

Question 17

Kinetochore

Answer 17

• Large complex of protein
• Microtubules (MTs) attach here through pro-metaphase
• MTs from each side of the cell attach to opposite sides

Question 18

What is the MicroTubule Organizing Center (MTOC) of the cell?

Answer 18

Centrosome

Question 19

Centrosome

Answer 19

• duplicated during S phase
• contains 2 centrioles
• nucleate spindle microtubules

Question 20

Centrioles

Answer 20

made of two bundles of MTs arranged at right angles

Question 21

Interphase MTs are reorganized into what?

Answer 21

mitotic spindle (attach to centromeres of chromosome during pro-metaphase)

Question 22

The three types of MTs in the mitotic spindle?

Answer 22

1.) Aster
2.) Kinetochore
3.) Interpolar

Question 23

Aster spindle

Answer 23

Anchor poles to cell periphery

Question 24

Kinetochore

Answer 24

Attach to chromosomes

Question 25

Interpolar

Answer 25

Interact with MTs from opposite pole (Kinesin)

Question 26

What pushes these MTs away from each other, producing tension across spindle?

Answer 26

Kinesin

Question 27

What initiates Prophase?

Answer 27

M-cyclin/Cdk complexes

Question 28

Phosphorylation by the M-Cdk causes?

Answer 28

- chromosome condensation - Mitotic spindle formation - Nuclear envelope breaks down releasing chromosomes into the cytoplasm

Question 29

What happens during Prophase?

Answer 29

- chromosomes condense and become visible - nuclear envelope - nucleolus disappears - Centrosomes move to opposite poles (and organize the formation of the mitotic spindle apparatus made of microtubules)

Question 30

What happens during Prometaphase?

Answer 30

- Nuclear envelope disintegrates completely - chromosomes begin to attach to spindle microtubules (dynamic process through which the chromosomes become attached equally to both mitotic spindles)

Question 31

What happens during Metaphase?

Answer 31

- Sister chromatids (aka chromosomes) line up at middle of cell at the metaphase plate - Spindle becomes fully formed - Chromosomes equally attached to both mitotic spindles

Question 32

Before Anaphase . . .

Answer 32

- Separation of the sister chromatids prevented by securin

Question 33

Securin is bound to and keeps what inactive?

Answer 33

Separase

Question 34

What is separase?

Answer 34

Enzyme that cleaves cohesins

Question 35

What happens during Anaphase once all chromosomes are attached to mitotic spindle?

Answer 35

Anaphase Promoting Complex (APC) is activated

Question 36

What is the Anaphase Promoting Complex?

Answer 36

a ubiquitin ligase - APC adds ubiquitin to securin, which equals destruction

Question 37

What happens with separase is activated during Anaphase?

Answer 37

- cuts cohesins at centromere - causes disjunction of sister chromatids

Question 38

What happens during Anaphase?

Answer 38

Sister chromatids separate at the centromeres - move towards the poles

Question 39

What happens during Telophase?

Answer 39

- Chromosomes arrive at the poles - Nuclear envelope reassembles - Chromosomes relax = indistinct chromatin again - Spindle disappears - Normal cellular function

Question 40

Late Telophase/Cytokinesis

Answer 40

process of dividing of the cytoplasm - cells pinch off and are separated - results in two daughter cells with identical chromosomes