Chapter 9 (Test 3) Flashcards
What is an orderly set of stages from the first division of a eukaryotic cell to the time the resulting daughter cells divide?
The Cell Cycle
When a cell is preparing for division it? (3)
It grows larger, the number of organelles doubles, and the DNA replicates.
The two major stages of the cell cycle are?
Interphase and Mitotic stage
Interphase consists of?
G1, S, and G2 phases
Most of a cell’s life is spent in _____, in which the cell performs its usual functions?
Interphase
_____ takes up 90% of the cell cycle?
Interphase
Time spent in interphase varies by ____?
Cell Type
_____ and ____ cells do not complete the cell cycle and remain in the G0 stage?
Nerve and Muscle
____ cells complete the cycle every few hours?
Embroyotic
The __ stage is just prior to DNA replication
G1
What happens in G1 phase? (4)
- Cell is in recovery from previous division
- Cell doubles its organelles
- Cell grows in size
- Cell accumulates raw material for DNA synthesis
What happens in S phase? (5)
- DNA replication takes place
- Proteins associated with DNA are Synthesized
- Chromosomes enter S phase with 1 chromatid each
- Chromosomes leave S phase with 2 identical chromatids (sister chromatids) each
- Sister chromatids remain attached until they are separated during Mitosis
What are two identical chromatids?
Sister chromatids
What happens in G2 phase? (2)
- G2 phase is located between DNA replication and onset of mitosis
- Cell division synthesizes proteins, including micro tubules, necessary for division
M stands for what in M stage?
Mitotic stage
What is is the entire cell division stage, including both mitosis and cytokinesis?
M stage (Mitotic stage)
What is Mitosis?
Nuclear division
Daughter chromosomes distributed by the mitotic spindle to two daughter nuclei
What is cytokinesis?
Division of the cytoplasm
During mitosis, daughter chromosomes are distributed by the _______ to two daughter nuclei.
Mitotic spindle
When division of the cytoplasm is complete (Cytokinesis) what is produced?
Two daughter cells
What is an agent that influences the activities of a cell?
Signal
What are growth factors?
Signaling proteins received at the plasma membrane
The cell cycle is controlled by what?
Internal and external signals
What are external signals?
Growth factors signaling proteins received at the plasma membrane
What are internal signals?
Family of proteins called cyclins that increase and decrease as the cell cycle continues
What are cyclins?
A family of proteins
What must be present for the cell to move from the G1 stage to the S stage, and from the G2 stage to the M stage?
Cyclin
The primary checkpoint of the cell cycle is the ___ checkpoint.
G1
DNA damage stops the cycle at the __ checkpoint by the protein ___
G1, p53
If the DNA is not repaired, p53 triggers _____ programmed cell death.
apoptosis
Another protein, ______, is responsible for interpreting growth and nutrient availability signals.
RB (retinoblastoma)
The cell cycle stops at the ___ stage if DNA has not finished replicating; stopping the cell cycle at this stage allows time for repair of possibly damaged DNA.
G2
The cycle stops if ______ are not properly attached to the mitotic spindle.
chromosomes
_____ is programmed cell death
apoptosis
_____ is caused by enzymes called caspases
apoptosis
Apoptosis is programmed cell death and involves a sequence of cellular events involving: (3)
- Fragmenting of the nucleus,
- Blistering of the plasma membrane, and
- Engulfing of cell fragments by macrophages and/or neighboring cells.
Apoptosis is caused by enzymes called _____
Caspases
_____ are released by internal or external signals.
Caspases
Cells normally hold _____ in check with inhibitors.
Caspases
Apoptosis and cell division are balancing processes that maintain the normal level of _______
somatic (body) cells
_______ is a normal and necessary part of development: frogs, for example, must destroy tail tissue they used as tadpoles, and the human embryo must eliminate webbing found between fingers and toes.
Cell death
Death by _____ prevents a tumor from developing
apoptosis
The G1 checkpoint: (1-6)
- After cell division occurs, cells enter G1 stage.
- After cell division occurs, cells enter G1 stage.
- Following the G1 stage, cells enter the G1 checkpoint to make sure that the correct conditions occur to continue to divide.
- Evaluating Growth signals
- Determining Nutrient Availability
- Assessing DNA Integrity
_____ is tightly regulated so that only certain cells in an adult body are actively dividing.
Cell division
After cell division occurs, cells enter ______
G1 stage
Following the ______, cells enter the _______ to make sure that the correct conditions occur to continue to divide.
G1 stage: G1 checkpoint
______ are sent to encourage or discourage cells from entering the cell cycle. Cells may enter a G0 stage, complete G1 and enter S stage.
Signal molecules
Cell division promoting signals can cause a _______ to add a phosphate group to RB, which is a regulator of the G1 checkpoint.
cyclin-dependent-kinase (CDK)
When RB is _______, the shape of RB changes and it releases the protein E2F, rather than binding to E2F.
phosphorylated
____ then binds to DNA and activates genes to complete the cell cycle.
E2F
If growth signals are sufficient, a cell will pass through the G1 checkpoint and _______ will occur.
Cell division
Cells require _____ prior to cell division
adequate nutrient levels
When nutrients are available, ___ bring about phosphorylation of RB, which releases E2F. E2F binds to DNA to produce proteins.
CDKs
When nutrients are not available, the cell enters the ______ and does not progress to the G1 stage.
G0 Stage
DNA must be free of errors and damage in order for ______ to occur.
Cell division