Cell Division

Question 1

What are the two phases of cell division?

Answer 1

Nuclear Division and Cytokinesis

Question 2

What are the types of nuclear division?

Answer 2

Mitosis & Meiosis

Question 3

What is the first step in both mitosis and meiosis?

Answer 3

Condensation of genetic material, chromatin, into chromosomes

Question 4

What are sister chromatids?

Answer 4

identical halves that make up a chromosome - the sister chromatids are joined at the centromere

Question 5

Describe interphase of the cell cycle

Answer 5

Cell division does not occur here - includes G0, G1, S, G2.

Question 6

When does replication and growth take place in the cell cycle?

Answer 6

S phase of interphase

Question 7

Describe the M Phase of the cell cycle

Answer 7

This is where cell division occurs - Mitosis (Prophase, Metaphase, Anaphase, Telophase) and Cytokinesis

Question 8

What happens in prophase?

Answer 8

Condensation - Nucleoli disappear and chromatin condenses into chromosomes. The nuclear envelope breaks down and mitotic spindle is formed. Microtubules connect to kinetochore and MTOCs move towards opposite poles.

Question 9

What happens in metaphase?

Answer 9

Alignment - chromosomes align across the metaphase plate and microtubules

Question 10

What happens in anaphase?

Answer 10

Separation - chromosomes separate into chromatids (which is referred to as a chromosomes now) - microtubules condense towards opposite poles until each pole has a complete set of chromosomes.

Question 11

What happens in telophase?

Answer 11

Restoration - Nuclear envelope is restored around each pole, forming two nuclei. Chromosomes within nuclei disperse into chromatin and nucleoli reappear —-Opposite of what happens in prophase.

Question 12

What is cytokinesis?

Answer 12

The division of the cytoplasm to form two cells.

Question 13

What structure is formed in plants following cytokinesis?

Answer 13

Cell plate. Vesicles from Golgi migrate to plane between two newly forming nuclei, fusing for form a cell plate which will become the plasma membranes for the two cells. Cell walls develop between membranes.

Question 14

What structure is formed in animals following cytokinesis?

Answer 14

Cleavage furrow. Microfilaments form a ring inside the plasma membrane between the two newly forming nuclei and pull plasma membrane to center, dividing the cell into two daughter cells.

Question 15

What is the difference between actin filaments and microfilaments?

Answer 15

Nada. Same shit. Microfilaments are made up of polymers of actin.

Question 16

Where and when does crossing over take place?

Answer 16

During synapsis at the chiasmata (close associations between non-sister chromatids of homologues) of Prophase I. This DOES NOT happen in Prophase II

Question 17

How does metaphase I differ from metaphase II?

Answer 17

(I). Homologous pairs of chromosomes are spread across plate - INDEPENDENT ASSORTMENT HAPPENS HERE

(II) Singular chromosomes are spread across the plate

Question 18

How does Anaphase I differ from Anaphase II?

Answer 18

(I). Homologues uncouple (II). Chromosomes separate into two chromatids

Question 19

How does Telophase I differ from Telophase II?

Answer 19

(I). Each pole contains half the number of chromosomes (uncoupled chromatids) - 2 haploid cells are formed. (II). Each pole contains half the number of chromosomes (chromatids) - 4 haploid cells are formed.

Question 20

What types of cells undergo mitosis?

What types of cells are produced?

Answer 20

Somatic cells, which are all body cells except those that produce eggs and sperm (or pollen)

Question 21

What types of cells undergo meiosis?

What types of cells are produced?

Answer 21

Reproductive cells (ovaries, testes, anthers) - gametes: eggs, sperm, pollen are produced.

Question 22

What is syngamy?

Answer 22

Fertilization - fusion of egg and sperm to give rise to a zygote

Question 23

What happens after zygote is formed?

Answer 23

The zygote undergoes mitosis to produce a multicellular organism.

Question 24

What are sources of genetic variation?

Answer 24

Crossing over (prophase I), Independent assortment (metaphase I), and joining of gametes

Question 25

What happens when (S/V) is high?

Answer 25

This means that the cell can function adequately because it has enough surface area for proper function and interaction with outside environment

Question 26

What happens when (S/V) is low?

Answer 26

This means the cell's volume has exceeded it's surface either cell growth stops of cell division begins.

Question 27

What happens to (G/V) as cell grows?

Answer 27

G/V decreases and because the cell has a finite amount of genetic material, the cell cannot be adequately supplied with enzymes and other biosynthetic substances.

Question 28

What are examples of cells that are genetically programmed not to divide?

Answer 28

Muscle and nerve cells - they remain in G0 rarely dividing after they have matured.

Question 29

What are the three checkpoints of the cell cycle and where do they occur?

Answer 29

G1 checks for DNA quality (end of G1). G2 checks for accuracy of DNA replication (at the end of G2). M (during metaphase) ensures microtubules are properly attached to all kinetochores at metaphase plate before ANAPHASE

Question 30

What are Cdks?

Answer 30

Cyclin-dependent kinases - enzymes responsible for advancing the cell past checkpoints and through the cell cycle. They activate other proteins by phosphorylating them.

Question 31

How are Cdks activated?

Answer 31

By the attachment of cyclins - and then complete activation by phosphorylation

Question 32

Describe the function of Mitosis-Promoting Factor (or maturation-promoting factor) (MPF)

Answer 32

MPF is a cyclin-Cdks complex that advances the cell cycle through G2 checkpoint.

Question 33

What are external factors that influence the cell cycle?

Answer 33

Growth factors (e.g. PDGF), density-dependent inhibition, anchorage dependence

Question 34

Why is cancer referred to as a disease of the cell cycle?

Answer 34

Transformed, cancerous cells, proliferate without regard to the cell cycle checkpoints, and other regulatory mechanisms.