Ch 12 - Cell Division

Question 1

Multicellular eukaryotes depend on cell division for:

Answer 1

• development from fertilized cell
• growth
• tissue repair

Question 2

System by which prokaryotes, mitochondria, and chloroplasts reproduce

Answer 2

Binary fission

Question 3

3 steps of binary fission

Answer 3

1) bacterial DNA (chromosome) replicated
2) cell elongates, pulling 2 copies of DNA apart
3) plasma membrane pinches inward, dividing the cell into 2

Question 4

When fully stretched, E. coli genomic DNA is _____ times as long as the cell

Answer 4

500

Question 5

Under optimal conditions, e. Coli cells divide every ___ minutes

Answer 5

20

Question 6

Genomic DNA of E. coli must be copied every ____ minutes, meaning ______ base pairs copied every second

Answer 6

20; 3866

Question 7

Genomic DNA of E. coli is attached to ______, near ___________

Answer 7

Plasma membrane; origin of replication

Question 8

Eukaryotic chromosomes

Answer 8

Contain more DNA than E. coli

DNA organized in separate chromosomes

Question 9

Chromatin

Answer 9

Complex of DNA and proteins

Question 10

Histones

Answer 10

Major proteins in chromatin

Question 11

Chromosome condensation

Answer 11

When chromosomes undergo several levels of coiling and become shorter, thicker and more compact
Reduces the length of chromatin by 10,000

Question 12

Cohesins

Answer 12

Proteins that attach chromatids

Question 13

Centromere

Answer 13

Constriction where sister chromatids are most closely attached

Question 14

Once sister chromatids are separated, the chromatids are called _______

Answer 14

Chromosomes

Question 15

3 steps of the cell cycle

Answer 15

1) DNA replication
2) mitosis
3) cytokinesis

Question 16

2 phases of the cell cycle

Answer 16

Mitotic phase (mitosis and cytokinesis)
Interphase (G1, S, G2)

Question 17

Stages of mitosis

Answer 17

Prophase
Prometaphase
Metaphase 
Anaphase 
Telophase

Question 18

Prophase

Answer 18

DNA in nucleus condenses
Becomes tightly packed until each pair of chromatids forms a distinct chromosome
Spindle fibers begin to form
2 nucleoli disappear

Question 19

Prometaphase

Answer 19

Chromosomes continue to condense
Nuclear membrane fragments
Microtubules of the spindle begin to attach to the sister chromatids

Question 20

Metaphase

Answer 20

Chromosomes align on equatorial plane of cell
Alignment occurs when spindle microtubules push and pull on the chromosomes
Stage where chromosomes are most condensed

Question 21

Anaphase

Answer 21

Shortest phase of mitosis
2 sister chromatids are pulled apart
-cohesion proteins are broken down
Spindle microtubules shorten as they break down at the 2 poles
Drags chromatids towards the poles
Cell elongates

Question 22

Telophase

Answer 22

Nuclear envelopes form around the separated chromosomes
Chromosomes become less condensed 
Nucleoli reappear
Spindle fibers break down
Mitosis complete

Question 23

Mitotic spindle

Answer 23

Forms in the cytosol during prophase
Consists of fibers made of microtubules and proteins
Assembly starts at the centromere (microtubule-organizing center)
Spindle microtubules grow out from centromeres toward equatorial plane

Question 24

Aster

Answer 24

Radial array of short microtubules extending from each centromere

Question 25

Kinetochore

Answer 25

Structure of proteins on each sister chromatid associated with specific sections of chromosomal DNA at the centromere
Spindle microtubules attach to kinetochores
Tug of war occurs and centrosome is pulled both ways

Question 26

Cytokinesis in animal cells

Answer 26

A ring of microfilaments forms around the equator of the cell
Ring contracts forming cleavage furrow

Question 27

Cytokinesis in plant cells

Answer 27

Cell wall is rigid and can’t be squeezed to make a cleavage furrow
New plasma membrane and cell wall are laid down on equatorial plane
-Cell plate: connects with existing plasma membrane and cell wall