Cell Cycle

Question 1

Cellular reproduction is essential:

Answer 1

– Creates new life
– Produce multi-cellular organisms
– Repair & renew cells

Question 2

mitosis

Answer 2

• somatic cellular division
• asexual
• results in two genetically identical daughter cells
• 2n→2n

Question 3

genome

Answer 3

specific genetic makeup of any organism

Question 4

chromosomes

Answer 4

DNA condensed around histone proteins

Question 5

somatic cells

Answer 5

body cells except for gametes

Question 6

chromatin

Answer 6

DNA relaxed inside of the nucleus of a non-dividing cell (“spaghetti”)

Question 7

sister chromatids

Answer 7

identical chromosomes separated during mitosis into each cell

Question 8

centromere

Answer 8

• joins sister chromatids together
• region of chromosomes composed of proteins
• spindle fibers attach to kinetochore of centromere

Question 9

binary fission

Answer 9

asexual prokaryotic replication

1. chromosome replication begins. one copy of the origin moves rapidly toward the other end of the cell.
2. replication continues. one copy of the origin is now at each end of the cell.
3. replication finishes. plasma membrane grows inward and new cell wall is deposited.
4. two daughter cells result.

Question 10

cell cycle

Answer 10

Events between time where cell divides
and rests
• Duration depends on the type of cell
• Muscle & nerve cells will never divide

Question 11

interphase

Answer 11

the cell grows and prepares for division by producing proteins and cytoplasmic organelles and replicating DNA; 90% of cycle

Question 12

G1 Phase

Answer 12

first gap - cell growth and organelle manufacture and normal functioning
-most variable in time for different types of cells (fast dividing: short phase, slow dividing: long phase)

Question 13

S Phase

Answer 13

DNA (chromatin) replication as cell continues to grow

Question 14

G2 Phase

Answer 14

second gap - cell prepares for division

• centrosomes have duplicated (ea with 2 centrioles)
• 1 or more nucleoli present in nuclear envelope

Question 15

prophase

Answer 15

• chromatin condense into chromosomes
• nucleoli disappear
• mitotic spindles (spindle apparatus) begin to form
• centrosomes move toward opposite poles

Question 16

prometaphase

Answer 16

-nuclear envelope fragments
• Microtubules enter middle of cell & begin attaching to chromosomes at kinetochores
• Nonkinetochore spindles interact with each other

Question 17

metaphase

Answer 17

• Chromosome meet in the middle of the spindle on the metaphase plate
-all sister chromatids are attached to kinetochore microtubules
• Longest phase of
mitosis

Question 18

anaphase

Answer 18

• Sister chromatids are pulled apart (each is now considered a chromosome)
• Chromosomes move to opposite poles due to microtubules
-nonkinetochore microtubules lengthen, elongating cell
• Shortest phase of mitosis

Question 19

telophase

Answer 19

– Nuclei begin to reform and nuclear envelopes arise from fragments
– Chromosomes begin to relax
– Mitosis is now complete

Question 20

cytokinesis

Answer 20

– The division of the cytoplasm

– Now you have two identical daughter cells

Question 21

cytokinesis in animal cells

Answer 21

A cleavage furrow create a shallow groove in the cell surface using a contractile ring of actin microfilaments

Question 22

cytokinesis in plant cells

Answer 22

Vesicles from the Golgi body move along microtubules to the middle of the cell to create cell plate

Question 23

G1 checkpoint

Answer 23

(aka restriction point) this is the most important & if passed usually results in complete cell division
-ensures that all external and internal condition are met for cell division
• If “no go” at this point the cell will enter G0 phase

Question 24

G2 Checkpoint

Answer 24

determines the cell is appropriately sized & DNA replicated correctly

Question 25

M Checkpoint

Answer 25

ensures all chromosomes are aligned during metaphase before anaphase
-each chromosome is attached to spindles and centromeres lined at metaphase plate

Question 26

skipping the M checkpoint would…

Answer 26

aneuploidy (incorrect # of chromosomes) and nondisjunction ex. Down syndrome

Question 27

cyclin-dependent kinases

Answer 27

– Enzymes that activate proteins by phosphorylating them
– Give the “go” signal at G1 & G2 checkpoints
– Constant amount found in the cell
– aka: cyclin-dependent kinases (Cdks)

Question 28

cyclins

Answer 28

– Transforms kinases into their active form

– Amount in cell fluctuates during cell cycle

Question 29

Maturation Promoting factor

Answer 29

Pushes cell past G2 checkpoint and into M phase
– Cyclin accumulates during G2 phase which activates MPF in turn starting mitosis by phosphorylating a variety of proteins in the nucleus causing fragmentation
– Switched off during anaphase by destroying its cyclin so nuclei can re-form during telophase

Question 30

proto-oncogenes

Answer 30

encode cyclin proteins

Question 31

tumor suppressor genes

Answer 31

produce proteins that signal cells when environmental conditions and DNA replication are not suitable for cell division and regulate apoptosis

Question 32

cell cycle control factors: internal

Answer 32

cdks to regulate checkpoints

Question 33

cell cycle control factors: external

Answer 33

– Proper nutrition and growth factors must be available for division (more important than density)
– Density-dependent inhibition: crowded cells stop dividing
– Anchorage dependence: cells must attach to a substrate in order to divide

Question 34

cancer

Answer 34

Cancer cells don’t respond to the body’s control of cell division resulting in the excessive dividing of cells
– They don’t need normal signals to stimulate division
– Growth isn’t inhibited by density dependence or anchorage dependence like normal cells
– After 20 to 50 division normal cells die, not cancer cells (ex: HeLa cells)

Question 35

cancer: transformation

Answer 35

Problem begins with transformation of a normal cell into a cancer cell
– Typically this is caught by your immune system, but if it goes undetected it can create a tumor

Question 36

cancer: benign tumor

Answer 36

– Cancerous cells stay at original site

Question 37

cancer: Malignant tumor

Answer 37

– Invasive cells that impair the functioning of one or more organs
– Have abnormal number of chromosomes
– Lose/destroy attachment to neighboring cells which allows for them to travel throughout the body resulting in metastasis

Question 38

Metastasis

Answer 38

1. tumor grows from a single cancer cell
2. cancer cells invade neighboring tissue
3. cancer cells spread through lymph and blood vessels to other parts of the body
4. small percentage of cancer cells survive and establish a new tumor in part of the body

Question 39

Treatment of Cancer: radiation

Answer 39

damages the DNA in cancer cells (more than normal cells) which are unable to repair the damage

Question 40

Chemotherapy

Answer 40

treatment of metastasis by using toxic drugs in the circulatory system
– Stops specific parts of the cell cycle to stop division
– Lots of side effects due to drug working on normal cells

Question 41

G0 Phase

Answer 41

nondividing state