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
If DNA damage is detected, CDK phosphorylates p53. Rather than being broken down, p53 levels in the nucleus ____
rise
The phosphorylated p53 binds to DNA to produce ______
DNA repair proteins
If DNA damage cannot be repaired, p53 levels continue to rise to trigger _____
Apoptosis
If DNA damage is repaired, p53 levels ____, and cell completes G1 stage as long as other requirements are met.
fall
A _________ contains a single double helix molecule composed of 50% protein
Eukaryotic chromosome
DNA and histone proteins are collectively called ______.
Chromatin
Histones: (5)
- Play a structural role
- Have essential survival functions
- Primarily 5 types
Responsible for DNA packing into nucleus
The five primary histone molecules: __, ___, ___, __ and __ are highly conserved beween species and have essential functions for survival.
H1, H2A, H2B, H3, and H4
The nearly ___ meters of DNA in a cell are packed into a nucleus _ micrometers in diameter.
two; 6
_____ are responsible for packaging the DNA so it can fit into such a small space.
Histones
The DNA double helix is wound around a core of ____ histone molecules, which appears like a string of beads
eight
Each bead (histone molecule) is called a _________ and they are joined by linker DNA.
Nucleosome
Nucleosomes joined together by _____ DNA appear as beads on a string.
“linker”
_______ represents the active chromatin that can be transcribed by RNA polymerase and transcription factors.
Euchromatin
The string is folder into a ____ structure, helped by histone H1.
zigzag
Darkly-stained fibers which can be seen in the nucleus are ______ and are more highly compacted than euchromatin and are rarely transcribed.
Heterochromatin
Research has shown that regulating the level of ________ of the DNA is a method of controlling gene expression in the cell.
compaction
When a cell is not undergoing division, DNA in the nucleus is a tangled mass of thin threads called ______.
chromatin
At cell division, ______ becomes highly coiled and condensed and is now visible as individual chromosomes.
Chromatin
Eukaryotic cell division involves _____ (nuclear division) and _____ (division of cytoplasm).
Mitosis; cytokineses
During mitosis, _________ are separated and distributed to daughter cells.
Sister chromatids
Before mitosis begins:
2
- Chromatin condenses (coils) into distinctly visible chromosomes.
- Each species has a characteristic chromosome number.
The ________ number includes two sets of chromosomes of each type.
diploid (2n)
Humans have __ different types of chromosomes.
23
The ________ is found in all the non-sex cells of an organism’s body (with a few exceptions).
diploid number
The ______ number contains one of each kind of chromosome.
haploid
In the life cycle of many animals, only ____ and ___ cells have the haploid number.
sperm and egg
Cell division in eukaryotes involves ______ and _____.
nuclear division and cytokinesis.
Somatic cells undergo ______ for development, growth, and repair.
mitosis
A chromosome begins cell division with two ______
sister chromatids
Sister chromatids are two strands of genetically identical _______.
chromosomes
At the beginning of cell division, they are attached at a ______, a region of constriction on a chromosome.
centromere
_______ are protein complexes that develop on either side of the centromere during cell division
kinetochores
The __________, the main microtubule organizing center of the cell, divides before mitosis begins.
centrosome
Each centrosome in an animal cell contains a pair of barrel-shaped organelles called ______
centrioles
The mitotic spindle contains many fibers, each composed of a bundle of __________
microtubules
Microtubules are made of the protein _______
tubulin
Microtubules assemble when ______ subunits join, disassemble when ______ subunits become free, and form interconnected filaments of cytoskeleton.
tublulin
_______ disassemble as psindle fibers form
microtubules
Mitosis is divided into five phases:
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
Prophase:
5
- Nuclear division is about to occur: chromatin condenses and chromosomes become visible.
- The nucleolus disappears and the nuclear envelope fragments.
- Duplicated chromosomes are composed of two sister chromatids held together by a centromere; chromosomes have no particular orientation in the cell at this time.
- The spindle begins to assemble as pairs of centrosomes migrate away from each other.
- An array of microtubules called asters radiates toward the plasma membrane from the centrosomes.
Prometaphase:
3
- Specialized protein complexes (kinetochores) develop on each side of the centromere for future chromosome orientation.
- An important event during prometaphase is attachment of the chromosomes to the spindle.
- The kinetochores attach sister chromatids to the kinetochore spindle fibers.
Metaphase:
3
- Chromosomes, attached to kinetochore fibers, are now in alignment at the metaphase plate, an imaginary plane that indicates the future axis of cell division.
- Non-attached spindle fibers, called polar spindle fibers, can reach beyond the metaphase plate and overlap.
- A cell checkpoint called the M checkpoint delays the start of anaphase until kinetochores are properly attached to the spindle fibers, and chromosomes are properly aligned along the metaphase plate.
Anaphase:
2
- The two sister chromatids of each duplicated chromosome separate at the centromere.
- Daughter chromosomes, each with a centromere and single chromatid, move toward opposite poles.
Telophase:
4
- The spindle disappears in this stage.
- The nuclear envelope reforms around the daughter chromosomes.
- The daughter chromosomes diffuse, again forming chromatin.
- The nucleolus reappears in each daughter nucleus.
_____ is division of the cytoplasm.
Cytokinesis
A _________indents the plasma membrane between the two daughter nuclei at a midpoint; this deepens to divide the cytoplasm during cell division.
cleavage furrow
Cytoplasmic cleavage begins as _______ draws to a close and organelles are distributed.
anaphase
The cleavage furrow deepens as a band of actin filaments, called the _________, constricts between the two daughter cells.
contractile ring
A narrow bridge exists between daughter cells during ________ until constriction completely separates the cytoplasm.
telophase
The rigid cell wall that surrounds plant cells does not permit cytokinesis by _______
furrowing
The Golgi apparatus produces vesicles, which move along the _________ to a small flattened disc that has formed.
microtubules
Vesicles fuse forming a ______; their membranes complete the plasma membranes of the daughter cells.
cell plate
______ permits growth and repair.
mitosis
In flowering plants, the _________ retains the ability to divide throughout the life of the plant; this accounts for the continued growth, both in height and laterally, of a plant.
the meristematic tissue
In mammals, ______ is necessary as a fertilized egg becomes an embryo and as the embryo becomes a fetus; throughout life, mitosis allows a cut to heal or a broken bone to mend.
mitosis
Many mammalian organs contain _________ (often called adult stem cells), which retain the ability to divide.
stem cells
Red bone marrow stem cells repeatedly divide to produce the various types of _______.
blood cells
__________ to produce human tissues can begin with either adult stem cells or embryonic stem cells.
Therapeutic cloning
Embryonic stem cells can be used for ____________, the production of a new individual.
reproductive cloning
There are two types of cloning:
reproductive cloning and therapeutic cloning.
Reproductive (somatic cell) cloning:
4
- In reproductive cloning, the donor cells are first starved, then the nucleus is taken out of the cell and transplanted into an enucleated egg.
- The donor cell stops dividing and goes into a G0 stage.
- Embryonic stem cells are formed and implanted into the embryo of a surrogate mother.
- When the embryo is fully developed, a clone is born.
Therapeutic cloning:
3
- One way to conduct therapeutic cloning is by the same procedure as reproductive cloning, embryonic stem cells are separated and subjected to treatment that causes it to develop into different types of cells: red blood cells, muscle cells, nerve cells.
- The other way to conduct therapeutic cloning is to use adult stem cells.
- One drawback to using adult stem cells is they are limited in the number of cell types they may become. However, researchers are trying to overcome this obstacle.
_____ is a cellular growth disorder that occurs when cells divide uncontrollably; i.e., cancer results from the loss of control and a disruption of the cell cycle.
Cancer
Most cancers begin as abnormal cell growth that is _____, or not cancerous
benign
When additional mutations occur, the growth becomes ______, or cancerous, and possesses the ability to spread.
malignant
Characteristics of cancer cells:
5
- Cancer cells lack differentiation
A. Unlike normal cells that differentiate into muscle or nerves cells, cancer cells have an abnormal form and are not specialized.
B. Normal cells enter the cell cycle only about 50 times; cancer cells can enter the cell cycle indefinitely. - Cancer cells have abnormal nuclei.
A. The nuclei may be enlarged and may have an abnormal number of chromosomes.
B. The chromosomes have mutated; some chromosomes may be duplicated or deleted. - Cancer cells do not undergo apoptosis
A. Whereas ordinary cells with DNA damage undergo apoptosis, cancer cells do not. - Cancer cells form tumors.
A. Normal cells are anchored and stop dividing when in contact with other cells; i.e., they exhibit contact inhibition.
B. Cancer cells invade and destroy normal tissue and their growth is not inhibited.
C. Cancer cells pile on top of each other to form a tumor. - Cancer cells undergo metastasis and angiogenesis.
A. A benign tumor is encapsulated and does not invade adjacent tissue.
B. Many types of cancer can undergo metastasis, in which new tumors form that are distant from the primary tumor.
C. Angiogenesis, the formation of new blood vessels, is required to bring nutrients and oxygen to the tumor.
Cancer cells pile on top of each other to form a _____
tumor
A ______ tumor is encapsulated and does not invade adjacent tissue.
benign
Many types of cancer can undergo ______ in which new tumors form that are distant from the primary tumor.
metastasis
_____, the formation of new blood vessels, is required to bring nutrients and oxygen to the tumor.
Angiogenesis
_________ code for proteins that stimulate the cell cycle and prevent apoptosis.
Proto-ocogenes
__________ code for proteins that inhibit the cell cycle and promote apoptosis.
tumor suppressor genes
Proto-oncogenes are at the end of a __________ from the plasma membrane to the nucleus; a growth factor binding at the plasma membrane can result in turning on an oncogene.
stimulatory pathway
Proto-oncogenes can undergo mutation to become _______(cancer-causing genes).
oncogenes
An ______ may code for a faulty receptor in the stimulatory pathway.
oncogene
________________ are at the end of an inhibitory pathway; a growth-inhibitory factor can result in turning on a tumor suppressor gene that inhibits the cell cycle.
tumor suppressor genes
Unicellular organisms reproduce via ________, in which the offspring are genetically identical to the parent.
asexual reproduction
____________ (bacteria and archaea) lack a nucleus and other membranous organelles.
prokaryotic cells
The ________ chromosome is composed of DNA and associated proteins, but much less protein than eukaryotic chromosomes.
prokaryotic
The chromosome appears as a ______, an irregular-shaped region that is not enclosed by a membrane.
nucleoid
_______ of prokaryotic cells produces two genetically identical daughter cells.
Binary fission
Before _______, DNA is replicated—both chromosomes are attached to a special site inside the plasma membrane
cell division
Both ______ and _____ ensure that each daughter cell is genetically identical to the parent.
binary fission and mitosis
