Chapter 10

Question 1

in prokaryotes cell division is by …

Answer 1

binary fission

Question 2

in eukaryotes cell division is by …

Answer 2

mitosis or meiosis

Question 3

Binary Fission in Prokaryotes:

Answer 3

-circular chromosome replicates, beginning at an origin and proceeding bidirectionally
-new chromosomes move to opposite ends (poles) of the cell
-septum divides the cell

Question 4

interphase 3 phases:

Answer 4

G1 phase, S phase, G2 phase

Question 5

G1 phase:

Answer 5

cell grows, possibly into a different kind of cell

Question 6

S phase:

Answer 6

DNA and certain other molecules replicate, 2 sister chromatids are produced from each chromosome

Question 7

G2 phase:

Answer 7

cell grows more to prepare for division, chromosomes condense

Question 8

Mitotic phase includes …

Answer 8

mitosis and cytokinesis

Question 9

chromosomes are composed of …

Answer 9

chromatin, heterochromatin, and euchromatin

Question 10

chromatin

Answer 10

a complex of DNA and proteins (histone proteins)

Question 11

heterochromatin is …

Answer 11

not expressed (not transcribed), tighter around histone protein

Question 12

euchromatin is …

Answer 12

expressed (transcribed regions = genes)

Question 13

chromosome

Answer 13

chromatin tightly bundle together

Question 14

nucleosome

Answer 14

DNA wrapped around a core of 8 histone proteins spaced 200 nucleotides apart

Question 15

Radial loops of the chromatin fiber are held in place by …, which in turn are aided …

Answer 15

scaffold proteins, condensing proteins

Question 16

homologous chromosomes

Answer 16

-have similar genes (alleles) at corresponding locations along the DNA molecule.
-for each one comes from the mother (via the egg) and the other from the father (via the sperm)

Question 17

chromatids

Answer 17

pair of homologous chromosomes that are connected at the centromere region by cohesin protein

Question 18

mitosis occurs in …

Answer 18

somatic cells

Question 19

Mitosis has 5 phases:

Answer 19

1. prophase
2. prometaphase
3. metaphase
4. anaphase
5. telophase

Question 20

proteins attached at the centromere

Answer 20

Kinetochore

Question 21

attach to the kinetochore

Answer 21

microtubules

Question 22

(microtubule-organizing centers) replicate and move to each end (pole) of the cell

Answer 22

centrioles

Question 23

prophase

Answer 23

• chromosomes further condense
• centrioles move to each pole
• spindle apparatus is assembled
• nuclear envelope dissolves
• homologous chromosomes pair and become chromatids

Question 24

prometaphase

Answer 24

• chromosomes become attached to the spindle apparatus by their kinetochores
• a second set of microtubules is formed from the poles to each kinetochore
• microtubules begin to pull each chromosome toward the center of the cell

Question 25

metaphase

Answer 25

- Microtubules pull the chromosomes toward the center of the cell - sister chromatids line up with centromeres on the metaphase plate (imaginary plane through the equator of the cell)

Question 26

anaphase

Answer 26

- removal of cohesin allows the centromeres to quickly separate - microtubules pull sister chromatids toward the poles

Question 27

telophase

Answer 27

- spindle apparatus disassembles - nuclear envelope forms around each set of sister chromatids - chromosomes begin to uncoil - nucleolus reappears in each new nucleus

Question 28

cytokinesis

Answer 28

- split cell into 2 - animals: actin filaments constrict to produce a cleavage furrow - plants: a cell plate forms between cells

Question 29

The cell cycle is controlled at three checkpoints:

Answer 29

1. G1/S checkpoint 2. G2/M checkpoint 3. late metaphase/early anaphase (spindle) checkpoint

Question 30

G1/S checkpoint

Answer 30

cell “decides” to replicate DNA

Question 31

G2/M checkpoint

Answer 31

cell “commits” to mitosis

Question 32

late metaphase/early anaphase (spindle) checkpoint

Answer 32

cell “ensures” that chromosomes are properly attached to the spindle before dividing

Question 33

cyclins

Answer 33

proteins produced in synchrony with cell cycle

Question 34

cyclin-dependent kinases (Cdks)

Answer 34

enzymes that drive the cell cycle; activated only when bound by a certain cyclin

Question 35

Growth factors

Answer 35

trigger intracellular signals that promote cell division

Question 36

cancer is a failure of cell cycle control resulting in ...

Answer 36

runaway cell division

Question 37

tumor-suppressor genes

Answer 37

normally prevent division in cells containing mutations

Question 38

proto-oncogenes

Answer 38

- normally code for growth factors or signal transduction proteins that promote normal cell division - normal genes that become oncogenes when mutated, and allow runaway cell division rather than normal (controlled) cell division - oncogenes can also cause cancer when they are introduced into a new cell (e.g., viral oncogenes)

Question 39

Two kinds of genes can cause cancer when they are mutated:

Answer 39

1. tumor-suppressor genes 2. proto-oncogenes

Question 40

mitosis purpose:

Answer 40

2N (diploid) splits and makes two 2N (diploid) that are genetically identical (daughter cells) to the mother cell