Factors that are needed to promote transcription may be accessed by the DNA of euchromatin.
Recent research shows that regulating the level of the DNA is an important method of controlling the expression of genes in the cell.
One can see dark-stained fibers under a microscope.
The areas within the nucleus are called Heterochromatin.
Depending on which parts of the chromosomes are being used more frequently, most chromosomes exhibit both levels of compaction.
Heterochromatin is considered inactive because the genes on it are rarely transcribed.
Prior to cell division, a scaffold helps condense the chromosomes into a form that is characteristic of metaphase chromosomes.
It's easier to move compact chromosomes than extended ones.
Start with a single DNA strand.
Discuss how human stem cells work.
Nuclear division and cytokinesis are the two main divisions of the cell in the eukaryotes.
The sister chromatids are separated from the daughter cells.
In Section 9.2, we noted that the genes in the chromosomes of eukaryotes are associated with a lot of different things.
When a cell is not undergoing division, the structure of the cell's genes is called euchromatin, and it has the appearance of a tangled mass of thin threads.
It is easy to see the individual chromosomes when the chromatin is coiled.
All cells have the same chromosomes that are found in the individual.
There are two chromosomes in the diploid number.
Most of the cells in animals are diploid.
The haploid number is half the diploid number.
There are only one chromosomes of each kind.
The egg and sperm of animals are examples of haploid cells.
Cell division must be made during interphase.
The arrangement includes replicating the chromosomes and duplicating the centrosome, which organizes the spindle apparatus necessary for the movement of chromosomes.
A 2n nucleus divides to produce daughter nuclei that are also 2n.
Nuclear division takes place when the chromosomes in the parent cell are duplicated.
During the S stage of interphase, this occurs.
There are two identical double molecule on each chromosomes.
Sister chromatids are attached to each other at the centromere.
The kinetochores are on either side of the centromere.
There are duplicate chromosomes.
A nucleus about to divide is depicted in the electron micrograph.
At the centromere, the chromatids are held together.
Each daughter has one double helix molecule.
The daughter cells have the same number of chromosomes as the daughter cells.
Each daughter nucleus gets a copy of the parent cell's chromosomes.
The main center of the cell divides before the start of the disease.
Centrioles are not found in plant cells and are found in animal cells.
The hollow cylinders are made of tubulin.
When tubulin subunits join, they become free once more.
The microtubules of the cytoskeleton break down.
This may allow the cell to change shape as needed for cell division, or it may provide tubulin for the formation of the spindle fibers.
For convenience of description, the process is divided into five phases: prophase, prometaphase, metaphase, and anaphase.
The red and blue chromosomes were passed on from one parent to the other.
The chromosomes are visible when the nuclear division is about to occur.
The number of centromeres in diagrammatic drawings gives the number of chromosomes.
The two centrosomes move away from one another as the spindle begins to assemble.
It is thought that asters brace the centrioles.
The chromosomes have no orientation because the spindle has not yet formed.
There are preparations for sister chromatid separation.
The center of the spindle will be where the fibers extend from the poles to the chromosomes.
The chromosomes are pulled from one pole to the other before they come into alignment, because the kinetochore fibers attach the sister chromatids to opposite poles.
The chromosomes are not in alignment even though they are attached to the fibers.
During the centromeres of chromosomes, there is a single plane at the center of the cell.
When viewed under a light microscope, the chromosomes appear to be straight across the middle of the cell.
It shows the future axis of cell division.
The start of anaphase is delayed until the kinetochores of the chromosomes are attached to the fibers of the metaphase plate.
The two sister chromatids of each duplicated chromosome separated at the centromere at the start of anaphase.
The daughter chromosomes, each with a centromere and single chromatid composed of a single double helix, appear to move toward opposite poles.
The poles are moving farther apart because the polar spindle fibers are moving past one another.
The motor molecule kinesin and dynein are involved in the sliding process.
The shortest phase is Anaphase.
The daughter nucleus has the same number of chromosomes as the original parent cell.
The polar spindle fibers are visible between the two nuclei.
After Page 154, the chromosomes become more diffuse and a nucleolus appears in each daughter nucleus.
The division of the cytoplasm requires cytokinesis.
The division of the cytoplasm is called cytokinesis.
Most cells havekinesis, but not all.
The result is a multinucleated cell.
Section 27.1 shows that the embryo sac in flowering plants is multinucleated.
The division of the cytoplasm does not reach completion until the following interphase begins.
Each newly forming cell is given a share of the cytoplasm that was duplicated during interphase.
During the previous interphase, the newly forming cells received a share of the cytoplasm.
The contractile ring slowly forms a constriction between the two daughter cells as the cleavage deepens.
The action of the contractile ring can be compared to pulling a rope around a balloon.
The material on either side of the constriction gathers in folds as the balloon relaxes in the middle.
A single cell is turned into two cells.
During telophase, a narrow bridge between the two cells can be seen, as the contractile ring separates the cytoplasm until there are two independent daughter cells.
Thekinesis in plant cells is different from thekinesis in animal cells.
The cell wall surrounds the plant cells.
The building of new cell walls between the daughter cells is what cytokinesis in plant cells involves.
During cytokinesis in a plant cell, a cell plate forms midway between two daughter nuclei.
There is a flattened disk between the two daughter plant cells near the site where the metaphase plate used to be.
It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 The Golgi apparatus produces vesicles, which move along the microtubules.
The is a new form of plasma that expands until it reaches the old one.
The Page 156 plant cell walls are formed by the release of molecules.
The primary cell walls are strengthened by the addition of fibrils.
The middle lamella fills the space between the daughter cells.
Growth and repair can be achieved with the help of matosis.
In both plants and animals, a single cell develops into an individual.
In plants, the individual could be a daisy or a fern, while in animals, the individual could be a human.
The ability to divide is retained in flowering plants.
The shoot tip accounts for an increase in the height of a plant for as long as it lives.
The ability of trees to increase their girth is accounted for by meristem.
As a fertilized egg becomes an embryo and as the embryo becomes a fetus, it is necessary for mitosis.
A child becomes an adult after birth.
It is possible for a cut to heal or a broken bone to heal.
In Section 9.1 you learned that the cell cycle is tightly controlled and that most cells of the body are permanently arrested in the G0 stage.
It is necessary to repair injuries, such as a cut or a broken bone.
Stem cells in mammals retain the ability to divide.
Red bone marrow stem cells divide multiple times to produce millions of cells that go on to become different types of blood cells.
Adult stem cells are being manipulated in the laboratory to produce different types of tissues.
The tissues could be used to cure illnesses.
The ability to clone an adult animal from a normal body cell has been achieved thanks to our knowledge of how the cell cycle is controlled.
Recent discoveries about how the cell cycle is controlled have led to the creation of both types of cloning.
Dolly the sheep showed that reproductive cloning is possible.
The cell's nucleus was placed in an enucleated egg after the donor cells were starved.
In therapeutic cloning, the goal is to produce mature cells of various cell types rather than an individual organisms.
The purpose of therapeutic cloning is to learn more about how specialization of cells occurs and to provide cells and tissues that could be used to treat human illnesses, such as diabetes, or major injuries like strokes or spinal cord injuries.
If the embryo were allowed to continue development, it would become an individual, which has ethical concerns about this type of therapeutic cloning.
The bone marrow has stem cells that can be used to make new blood cells.
Adult stem cells are limited in their number of cell types.
Scientists are starting to create iPS cells to mimic embryonic stem cells.
Experiments have led to a strategy that allows creation of iPS cells without using an embryo or stem cell.
Scientists stressed regular adult cells with trauma, low oxygen, and high acidity instead of altering genes or swapping nuclei.
The cells survived by reverting back to an embryo state.
They were able to divide and differentiate into new cell types.
The purpose of reproductive cloning is to produce an individual that is genetically identical to the one that donated a nucleus.
The nucleus is placed in an enucleated egg and the embryo is implanted into a surrogate mother for further development.
Clones are used to produce specialized tissue cells.
The nucleus is placed in an enucleated egg and after several divisions, the embryonic cells are separated and treated to become specialized cells.