Cell Division and Mitosis Study Guide

What is a gene?

A unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

What causes cancer? Does it make cells divide slower or quicker? What are tumors?

Cancer is a complex group of diseases with many possible causes. Some are Smoking, Tobacco, Diet, Physical Activity, Sun and Other Types of Radiation, Viruses and Other Infections. These causes as well as cancer make the cells divide quicker. Tumors are the abnormal growth of body tissue. Some tumors can be cancerous and some tumors are noncancerous.

In which part of the cell do we find the chromosomes? Which important molecule (3 letters) is found on the chromosomes?

Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). DNA is the important molecule found on the chromosomes.

Colchicine is a chemical that when applied to a cell during mitosis can be used to "freeze" cells in metaphase by preventing the chromosomes from moving away from the metaphase plate. What part of the cell does colchicine most likely affect?

Colchicine inhibits the formation of the microtubules or spindle fibers. Without the spindle fibers the chromosomes cannot move to the poles.

What happens during the G0 phase? What kind of cells stay in this phase?

During the G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle. The cell cycle machinery is dismantled and cyclins and cyclin-dependent kinases disappear. Some examples of cells that enter G0 and stay forever are nerve cells and heart cells. This is because once they reach maturity, nerve and heart cells do not divide again, so they stay in the G0 phase.

What are three phases of interphase (in order), and what happens during them?

Interphase is composed of G1 phase (cell growth), followed by S phase (DNA synthesis), followed by G2 phase (some more cell growth). At the end of interphase comes the mitotic phase, which is made up of mitosis and cytokinesis and leads to the formation of two daughter cells. In G1 phase (Gap 1) the phase occupies the time between the end of cell division in mitosis and the beginning of DNA replication during S phase. During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the centrosomes undergo replication. During the S phase (Synthesis) the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase (Mitosis). During the last phase, G2 (Gap 2) The cell has grown, DNA has been replicated, and now the cell is almost ready to divide. This last stage is all about prepping the cell for mitosis or meiosis. During G2, the cell has to grow some more and produce any molecules it still needs to divide.

Name the phase that lasts the longest.

Interphase is the phase that lasts the longest, because when the cell grows and copies its DNA before moving into mitosis. During mitosis, chromosomes will align, separate, and move into new daughter cells. The prefix inter- means between, so interphase takes place between one mitotic (M) phase and the next.

How is each chromosome attached to its duplicate?

It is attached to its duplicate by the Centromere. The primary function of the centromere is to provide the foundation for assembly of the kinetochore, which is a protein complex essential to proper chromosome segregation during mitosis. In electron micrographs of mitotic chromosomes, kinetochores appear as platelike structures composed of several layers

What is the original chromosome and duplicate called?

It is called the ​Chromatid. During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes. Following DNA replication, the chromosome consists of two identical structures called sister chromatids, which are joined at the centromere.

What is mitosis? What is the goal of mitosis?

The goal of mitosis is to divide a cell to produce two cells, each of which is identical to the parent cell. a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

What are spindle fibers? When do they form?

The spindle fibers provide a framework and means of attachment that keep chromosomes organized, aligned and assorted during the entire process of mitosis, lessening the occurrence of aneuploidy, or daughter cells with incomplete sets of chromosomes.

How many phases are in mitosis? Name them in order, and describe what happens in each phase.

Today, mitosis is understood to involve five phases, based on the physical state of the chromosomes and spindle. These phases are Interphase prophase, prometaphase, metaphase, anaphase,telophase, and Cytokinesis. Interphase is the portion of the cell cycle that is not accompanied by observable changes under the microscope, and includes the G1, S and G2 phases. During interphase, the cell grows (G1), replicates its DNA (S) and prepares for mitosis (G2). Prophase is the first stage of cell division, before metaphase, during which the chromosomes become visible as paired chromatids and the nuclear envelope disappears. The first prophase of meiosis includes the reduction division. Prometaphase is the second phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. During prometaphase, the physical barrier that encloses the nucleus, called the nuclear envelope, breaks down. Metaphase is a stage in the cell cycle where all the genetic material is condensing into chromosomes. These chromosomes then become visible. During this stage, the nucleus disappears and the chromosomes appear in the cytoplasm of the cell. Anaphase is the stage of meiotic or mitotic cell division in which the chromosomes move away from one another to opposite poles of the spindle. Telophase is the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed. Cytokinesis is the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.

What controls the cell cycle?

Two groups of proteins, called cyclins and cyclin-dependent kinases (Cdks), are responsible for the progress of the cell through the various checkpoints. Cyclins regulate the cell cycle only when they are tightly bound to Cyclin-dependent kinases.

If the parent cell has 10 chromosomes, how many will each of the daughter cells have?

Two. There will be two daughter cells at the end of mitosis. Each will have 10 chromosomes, if the parent cell has 10. The chromosomes will not have sister chromatids because after mitosis, the duplicated pairs have separated into the two daughter cells. The cells will each be diploid, just as the parent cell was.

How many chromosomes do the cells (except mature egg & sperm cells aka gametes) in our body (somatic cells) have?

We have 46, because we get 23 from our mom and 23 from our dad.