question

cell cycle

answer

the process in which a cell grows, prepares for division & divides to create a copy of itself..there are two parts to cell cycle: Interphase and the M- phase .

question

Why do cells divide?

answer

The larger the cell becomes, the more demands are placed on its DNA and the less efficient its nutrient/waste exchange is. Cells divide to counteract these problems.

question

what happens to a cell's surface area to volume ratio as a cell increases in size? why is this bad and why does this happen?

answer

The surface area to volume ratio decreases as a cell increases in size because the volume increases faster than the surface area. It's bad because a decrease in surface area means the cell can't efficiently exchange food and waste with its surroundings.

question

asexual versus sexual reproduction

answer

cell division is sexual reproduction in many single celled organism. asexual reproduction is the production of gentically identical offspring from a parent. sexual reproduction is the production of gentical different ofspring from a parnet through the fusion of parent cells.

question

When a cell is preparing for division what does it do?

answer

It grows larger, the number of organelles doubles and DNA duplicates;

question

interphase

answer

the phase where a cell spends most of its life carrying out normal cell function. during interphase the cell will grow and prepare for cell division. The time spent in interphase varies from cell to cell. Interphase consist of three stages G1, S and G2.

question

G1 stage

answer

the stage just before DNA replication; during this stage the cell increases in size, doubles in organelles, and accumulates material for DNA replication. Some cells enter a phase within G1 called Go.

question

Go stage:

answer

a stage within G1 where cell cycle is suspended; the cell continues to perform everyday processes but no preparations are made for cell division; muscle and nerve cells typically go through Go stage.

question

S stage

answer

stage that follows G1 where DNA replicates which duplicates the chromosomes. At the beginning of S stage, each chromosome is composed of one DNA double helix. DNA replication results in duplicated chromosomes. After replication, each of the duplicated chromosomes are referred to as chromatids.

question

G2 stage

answer

stage that follows S and last until just before cell division(mitosis). During this phase the cell synthesizes proteins that form microtubules. which will be used during the mitotic stage.

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M stage

answer

stage devoted to cell division. M stage includes both mitosis and cytokinesis; once division of the cytoplasm is complete, two daughter cells are produced.

question

cytokinesis

answer

division of the cytoplasm;

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mitotic spindle

answer

protein structure that is responsible for distributing daughter chromosomes to the daughter nuclei;

question

chromatid

answer

one copy of a duplicated chromosome;

question

signal t

answer

an agent that influences the activities of a cell. In general, signals ensure that the cell cycle stages proceed in normal sequence. Signal molecules are sent to encourage or discourage cells from entering the stages of the cell cycle •

question

what two types of regulatory proteins control cell cycle? Describe

answer

The cell cycle is controlled by regulatory proteins inside and outside of the cell. Internal regulators respond to events inside the cell. Generally, these cells regulate whether the cell will continue to the next cell cycle phase. For example, if chromosomes haven't been duplicated in S phase a regulatory protein will not allow the cell to enter mitosis. External regulators respond to events outside the cell. These regulatory proteins direct the cell cycle to speed up, slow down or stop.

question

growth factors

answer

a family of external regulatory protein signals received at the plasma membrane that stimulate the growth & cell division. The regulators are important in embryonic development & wound healing.

question

Explain cell checkpoints

answer

a point in the cell cycle where the cell will either stop or continue depending on what internal signals it receives; there are three checkpoints in a cell's cycle.

question

cyclins

answer

a family of internal signaling proteins that regulates cell cycle. the amount of cyclin present in the cell will either increase or decrease as the cell cycle continues; specific cyclin must be present for the cell to proceed from G1 to S and from G2 to M.

question

G1 checkpoint

answer

this is the cell cycle's main checkpoint; G1 checkpoint ensures that conditions are right for cell division by evaluating growth signals, determining the availability of nutrients and assessing the integrity of DNA. If any of these criteria are not met, the cell will halt cell cycle activity and enter Go or undergo apoptosis. Otherwise the cell commits to divide when growth signals & nutrients are present;

question

what condition will stop the cycle at G1 checkpoint?

answer

damage to DNA only. Lack of nutrients encourage cell to enter G0.

question

p53

answer

signaling protein molecule that stop the cell cycle at G1 checkpoint if DNA is damaged; p53 initiates DNA repair. If DNA is not fixed then more p53 accumulates triggering apoptosis(cell death);

question

RB

answer

retinoblastoma: a protein that is responsible for interpreting growth signals and nutrient availability signals;

question

G2 checkpoint

answer

sometimes called mitosis checkpoint; the cell cycle stop at the G2 stage if DNA has not finished replicating; stopping the cell cycle here allows time for repair of possibly damaged DNA; also, the cell cycle will stop here if chromosomes are not properly attached to the mitotic spindle; mitosis will occur if DNA has replicated properly and/or spindle is properly attached to chromosomes. If not, apoptosis happens;

question

M checkpoint

answer

spindle assembly checkpoint. mitosis will not continue if chromosomes are not properly aligned;

question

apoptosis

answer

programmed cell death that happens in the following sequence: (1) Cell separates from neighboring cells. (2) the nucleus fragments (3) plasma membrane blisters and cell breaks into smaller fragments (4) cell fragments are engulfed by white blood cells/ or neighboring cells.

question

Caspases

answer

an enzyme that cause apoptosis; these enzymes are always present in the cell and are normally held in check by inhibitors but can be unleashed by either internal or external signals;

question

Does apoptosis and cell division complement each other? How?

answer

Apoptosis and cell division are balancing processes that maintain a normal amount of body cells in living organisms; if cells never died, organisms would have an ever increasing number of cells because cell division happens every second of life;

question

What is a natural way the human body prevents the spread of cancer cells?

answer

Apoptosis

question

What will growth signals that promote cell division do?

answer

Growth signals that promote cell division cause a cyclin-dependent kinase (CDK) to add a phosphate group to RB. When RB is phosphorylated, its shape changes, causing it to release E2F. E2F binds to DNA and activates certain genes whose products are needed to complete the cell cycle.

question

What happens when nutrients are and are not available in cells?

answer

When nutrients are available cyclin-dependent kinase (CDK) phosphorylates RB. When they are not available, the cell enters Go stage and does not progress to G1.

question

What happens if DNA damage is detected?

answer

CDK (cyclin-dependent kinase) phosphorylates p53. Rather than being broken down, p53 levels in the nucleus rise. The phosphorylated p53 binds to DNA, activates a gene that produces DNA repair proteins. If DNA damage cannot be repaired, p53 levels continue to rise and trigger apoptosis. If DNA is repaired, p53 levels fall off and the cell completes G1 stage as long as other requirements are met.

question

histones

answer

proteins associated with DNA that function to organize chromosomes

question

** chromatin

answer

threadlike material made up of DNA, RNA, and protein; chromatin is the uncondensed & uncoiled version of chromosomes; under a microscope chromatin appears threadlike of grainy; chromatin is located in the nucleoplasm of the nucleus; chromatin is present when a cell is not undergoing division

question

* chromosomes

answer

rodlike structures made up of DNA, RNA, and proteins(same components as chromatin) formed during cell division just before the cell divides; chromosomes are condensed, coiled and folded chromatin.

question

diploid (2n) number

answer

the full number of chromosomes that are found in all the non-sex cells of an individual; the diploid number includes two chromosomes of each kind;

question

haploid (n) number

answer

half the diploid number; the habloid number contains only one chromosome of each kind. In the life cycle of many organisms, only sperm and egg cells have the haploid number.

question

** centrosome

answer

an organelle that serves as the main microtubule organizing center for animal cells as well as a regulator of cell-cycle progression; it organizes the spindle apparatus necessary for movement of chromosomes. before mitosis begins, it divides

question

**mitosis

answer

also known as karyokinesis; division of the nucleus; process where a 2n nucleus divides to produce two new identical 2n nuclei. the original cell(nucleus) is called the parent cell and the two news cells are commonly referred to as daughter cells. Mitosis is divided into 4( or 5 depending on teacher) phases: (1) prophase, metaphase, anaphase and telophase;

question

sister chromatids

answer

identical copies of a duplicated chromosome that have not been pulled apart and are connected at their centers

question

centromere

answer

the region of attachment between two sister chromatids;

question

kinetochore

answer

protein complexes that develop on either side of the centromere during cell division; kinetochores are important to help orientate the chromosome in later steps of mitosis;

question

In terms of chromosomes, how does a cell begin mitosis?

answer

A cells enter mitosis with duplicated chromosomes. Each of the duplicated chromosome is called a chromatid. Even though the chromosomes have been duplicated (producing two sister chromatids) we still consider the two chromatid structure a single chromosome because they are still connected together. When the sister chromatids are pulled apart and placed in he daughter cell, they will return to being called chromosomes.

question

*centrioles

answer

short cylinders with a 9 + 0 pattern of microtubule triplets(nine sets of triplets arranged in an outer ring. the center of the centriole does not contain any microtubules); in animals cells and most protist, the centrosome has two centrioles lying at right angles to each other; plant and fungal cells have the equivalent of a centrosome but no centrioles; in cells with cilia and flagella, centrioles are believed to give rise to basal bodies;

question

**mitotic spindle

answer

protein structure that is responsible for distributing daughter chromosomes to the daughter nuclei; it is organized by the centrosome and is made of many fibers. Each fiber is composed of a bundle of microtubules;

question

* microtubules

answer

largest filaments of the cytoskeleton that are hollow cylinders made of globular proteins called tubulin. This tubulin can occur as alpha or beta tubulin; when microtubules are assembled they come together as dimers. These dimers have the ability to arrange themselves into rows. They disassemble when tubulin subunits becomes free, and form interconnected filaments of cytoskeleton. microtubules disassemble as mitotic spindle fibers form. Regulation(ability to turn a process on or off) of microtubule assembly is under the control of the microtubule organizing center (MTOC); the main MTOC is the centrosome; the main function of microtubules is to maintain the shape of the cell and act as tracks along which organelles can move.

question

prophase

answer

first phase of mitosis; prophase is subdivided into two categories: (early) prophase and prometaphase(late prophase); during (early) prophase the following events take place: (1) chromatin condenses becoming visible structures called chromosomes; (2) the nucleolus disappears & the nuclear envelope fragments; (3) mitotic spindle begins to assemble as the two centrosomes migrate away from one another;In the later stages of prophase(prometaphase) the following events take place: (1) specialized protein complexes called kinetochores develop on each side of the centromere (2) chromosomes attach to the spindle fibers(these spindle fibers are called kinetochore spindle fibers) and begin to move towards the metaphase plate;

question

kinetochore

answer

specialized protein complexes that develop on each side of the centromere; kinetochores are necessary for future chromosome orientation;

question

kinetochore spindle fibers

answer

microtubule fibers connected to the kinetochore;

question

polar spindle fibers

answer

microtubule fibers connected two one of the two poles in a dividing cell;

question

metaphase

answer

(1)chromosomes(attached to kinetochore fibers) align on a single plane at the center of the cell(metaphase plate). (2) non-chromosome attached spindle fibers(called polar spindle fibers) reach beyond the metaphase plate and overlap; (3) M checkpoint delays the start of Anaphase until chromosomes are properly aligned along the metaphase plate;

question

anaphase

answer

Mitotic spindle fibers shorten pulling sister chromatids apart towards the opposite poles of the cell. at the centromere to become the chromosome of each daughter cell. Daughter chromosomes move towards opposite poles of the cell. Depending on the type of cell cytokinesis may or may not begin.

question

telophase

answer

mitotic spindle disappears; nuclear envelope reforms around daughter chromosomes. Chromosomes unfold and decondense to form chromatin;

question

**cytokinesis

answer

division of the cytoplasm; division of the cytoplasm begins in anaphase, and doesn't end until interphase; cytokinesis happens in most cells but not all and proceeds differently in plant and animal cells;

question

cleavage furrow

answer

an indentation of the membrane between two daughter nuclei;

question

cytokinesis in animal cells:

answer

a cleavage furrow indents the plasma membrane between the two daughter nuclei at a midpoint; the cleavage furrow deepens as a band of actin filaments, called the contractile ring constrict between the two daughter cells. A narrow bridge between the two daughter cells can be seen until the contractile ring continues to separate the cytoplasm until there are two independent daughter cells.

question

cytokinesis in plant cells

answer

the rigid cell walls that surround plant cells do not permit cytokinesis via cleavage furrow; when plants are ready to undergo cytokinesis a small, flattened disk appears between the two daughter cells near the site where the metaphase plate once was. The glogi apparatus produces vesicles which move to the region where the disk is. As more vesicles arrive the fuse together and form a new membrane called the cell plate; the cell plate expands outward until it reaches the old plasma membrane and fuses with this membrane. The new membranes releases molecules that form new plant cell walls.

question

How is mitosis used in flowering plants?

answer

Meristematic tissue in plants use mitosis to allow the plant to grow in both height and girth(laterally);

question

What is true about most adult body cells?

answer

Most cells of the body at adulthood are permanently arrested in G0 stage. Adult stem cells are used by the body to replace damaged cells;

question

adult stem cells:

answer

cells found in organs and tissue that retain their ability to divide;

question

Therapeutic cloning

answer

a procedure used to produce human tissues;

question

reproductive cloning

answer

a procedure used to create a new individual.

question

During what phase of mitosis is the DNA replicated?

answer

It's not replicated during mitosis. This happens during Synthesis phase of Interphase

question

Distinguish between chromosome, chromatin, chromatid, centriole, cytokinesis, centromere and kinetochore.

answer

Chromatin is the chromosome before its undergone cell division. So it is an uncondensed tangled mass of a histone and DNA double helix. A chromosome is made of the same things as chromatin, except now the DNA is supercoiled and condensed(DNA is tightly linked to histone).A chromosome is the stage where genetic material of DNA is packaged in a way that it is ready for cell division process. Usually a chromosome is composed of one DNA double helix. After DNA replication, the chromosome will have duplicated and now there will be will two identical DNA double helix molecules. A chromatid is one of the the identical DNA double helixes inside the duplicated chromosome structure. The two chromatids are held together. This site in the middle were the chromatids are linked is called the centromere. Kinetochores are the proteins that develop on each side of the centromere during cell division. The centrosome is the main microtubule organizing center of the cell; it will divide before mitosis. The centrosome is made up of barrel shaped organelles called centrioles.

question

Describe the preparation for mitosis:

answer

DNA replication; doubling of organelle count; division of the centrosome;

question

How do plant cell mitosis differ from animal cell mitosis?

answer

Their cytokinesis is different; Centrosomes of plants do not have centrioles while animals do; Aster brace centrioles during later stages of mitosis

question

what is the purpose of mitosis?

answer

Formation of duplicate cells..parent cell no longer exist; parent is now two different daughter cells

question

cancer

answer

un[regulated] or uncontrolled cell growth a disorder in which body cells lose the ability to control cell growth & divide uncontrollably. It has been hypothesized that cancer is caused by the accumulation of mutagens that cause a loss of control of the cell cycle.

question

tumor

answer

a mass of cancer cells that form an abnormal growth.

question

what affects do cancer cells have on the body?

answer

As the cancer cells spread, they absorb nutrients need by other cells, block nerve connection and prevent the oorgans they invade from functioning properly.

question

what causes cancer?

answer

Cancer is caused by defects in the genes that regulate cell growth & division. There are several sources that can cause these defects: nuclear radiation exposure, smoking, tobacco(chewing or smoking) and other defective genes.

question

what defect do many cancer cells have in common?

answer

An astonishing number of cancer cells have a defect in a gene called p53. normal p53 codes for a protein that stops cell cycle if their is damage to DNA.

question

what are some common treatments for cancer?

answer

[1] surgical removal of cancer. treatment is usually used for skin cancer. [2] exposure to high energy radiation. [3] chemotherapy: the use of chemical compund to kill or slow cancer cell growth. it should be noted that chemotherapy also kills healthy cells and for this reason has serious side effects.

question

benign

answer

non-cancerous.

question

malignant

answer

cancerous cells that possess the ability to spread;

question

What major characteristics of cancer cells distinguish them from normal cells?

answer

(1)Cancer cells lack cell differentiation (the ability of a cell to perform a specific function) like muscle or nerve cells. cancer cells do not perform the function of the cells that surround them. (2) They have abnormal nuclei. the nuclei of cancer cells are larger than normal cells & contain chromosomes that have deleted sections or extra copies; often the nuclei of cancer cells will contain an abnormal number of chromosomes. (3) Cancer cells do not undergo apoptosis. Whereas normal cells with DNA damage undergo apoptosis, cancer cells do not. (4) Cancer cells form tumors: Normal cells are anchored and stop dividing when in contact with other cells; they exhibit contact inhibition; cancer cells do not do this. Cancer cells do not stop growing. They pile on top of each other forming layers of cancer cells called tumors. (5) Cancer cells undergo metastasis and angiogenesis

question

metastasis

answer

the spread of tumor cells throughout different parts of the body;

question

angiogenesis

answer

the formation of new blood vessels to supply the growing tumor with more nourishment;

question

What are the usual steps in the development of a malignant tumor from a benign tumor?

answer

Malignant cells form when benign cancer cells undergo mutation and stop being regulated by control.

question

proto-oncogenes

answer

normal genes that code for proteins which promote progression through the cell cycle. they stimulate cell cycle, prevent apoptosis and are the last step of a signal stimulatory pathway; proto-oncogenes are often compared to a gas pedal in a car because they cause the cell cycle to go or speed up;

question

oncogenes

answer

cancer causing genes; genes that are formed when a proto-oncogene experiences a mutation; oncogenes are under constant stimulation and keep promoting the cell cycle regardless of the circumstances; if proto-oncogenes are likened to a gas pedal, oncogenes can be likened to pressing the gas pedal and never letting go.

question

tumor-suppressor genes

answer

normal genes that code for proteins that inhibit the cell cycle and promote apoptosis; they are the last step of a signal inhibitory pathway; tumor-suppressor genes are comparable to the brakes of a car;

question

Compare and contrast the effect on the cell cycle of (a) mutation in a proto-oncogene to (b) a mutation in a tumor suppressor gene.

answer

mutations in either of these genes can cause cancer. A mutation in a proto-oncogene turns the gene into an Oncogene and will result in a promoted cell cycle regardless of circumstances; this is comparable to pressing the gas pedal and never letting go; uncontrolled cell division will occur... tumor suppressor genes become inactive; a mutation in a tumor suppressor gene is much like brake failure in a car. a tumor suppressor gene mutation results when the mechanism that slows down or stops cell division does not function.

question

What oncogenes are frequently involved in human cancers?

answer

genes in the ras gene family cause most human cancer; breast & ovarian cancer are caused by mutant forms of BRCA1(breast cancer predisposition gene 1);

question

What tumor suppressor genes are frequently involved in human cancer?

answer

Mutations to tumor genes that code for RB and p53... RB and p53 genes are called tumor suppressor genes

question

What is the effect of chemotherapy drugs?

answer

To inhibit the formation of the mitotic spindle...while these drugs can affect normal cells, they affect cancer cells first because cancer cells reproduce quicker.

question

embryo

answer

1] an organism in the early stages of development[growth & differentiation. 2] a developing organism

question

differentiation

answer

process by which cells become specialized to carry out a specific function. For example, differentiation can result in an immature cell becoming any number of different cells types such as nerve, muscle or immune cell.

question

stem cells

answer

cells that can differentiate into any cell type.

question

totipotent

answer

the ability to transform[differentiate] into any cell type in the body. only the fertilized eggs & the cells of early embryonic development are totipotent.

question

blastocyst

answer

a structure that forms in the early stages of embryo development after fertilization. It is a thin-walled hollow structure containing a cluster of cells called the inner cells from which the embryo will develop. the outer cells will form tissue that will attach the embryo to its mother

question

pluripotent

answer

the ability of a cell to develop into many but not all cell types in the body. The embryo that develops from the inner cell mass of the blastocyst is considered pluripotent.

question

what is the difference between embryonic & adult stem cells?

answer

embryonic stem cells are pluripotent while adult stem cells are multipotent. the function of adult stem cells are to renew and replace adult body cells.

question

Give some examples of locations of adult stem cells and there function

answer

1]bone marrow: stem cells here develop into blood cells. 2] brain; stem cells in the brain can produce neurons or nerve cells.

question

multipotent

answer

ability to devlop into a limited number of cell types.

question

what are the pros and cons of embryonic stem cell research?

answer

PRO Embryonic stem cells may be used to replace damaged cells from heart attacks, strokes and spinal cord injuries. CON Harvesting stem cells from embryos damages the embryo resulting in embryo death, creating an ethical issue on rights to life.

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