Mitotic Cell Cycle - Session 2

In Asexual reproduction, a single parent organism produces offsprings that are genetically identical or very similar to itself. It is common in plants and single celled organisms. Do you know how bacteria grow in their population? They do it through binary fission. Binary fission is a common form of Asexual reproduction. It is observed in bacteria and amoebas. During binary fission, the parent cell duplicates its genetic material. It then divides into two identical daughter cells. Each daughter cell then grows and eventually separates into independent organism.

Budding is another method of Asexual reproduction. It is seen in many plants and animals. It involves the formation of a bud or an outgrowth on the parent organism. The bud grows and develops into a genetically identical or similar individual. Once the bud matures, it detaches from the parent and becomes a fully functional organism. Examples of organisms that reproduce by budding include yeast, hydra, and some plants like cacti.

Mitosis helps in repairing the tissues. It helps in replacing the damaged or dead cells with new ones. When tissues are damaged, the body sends signals to particular cells called fibroblasts and immune cells. These cells release chemical signals that tell nearby cells to divide and make new cells.

Telomeres are specialized structures located at the ends of chromosomes. They are made of DNA sequences. Telomeres are like protective caps. They help keep our chromosomes stable during cell division. Each time our cells divide, a small part of the telomeres gets lost, which is normal. But over time, telomeres become shorter and shorter. When telomeres become very short, our cells stop dividing. This is a good thing because it prevents damaged or unstable cells from multiplying out of control. This uncontrolled multiplication of cells could result in cancer.

Stem cells are special cells in our bodies that can develop into different types of cells. They can divide and make more copies of themselves. They can also change into other specific cells with specific jobs. Stem cells are important for the growth and repair of our bodies. There are different kinds of stem cells. We shall discuss embryonic stem cells.

Embryonic stem cells come from the inside of a growing embryo at an early stage. These cells are very special because they can turn into any type of cell in our bodies. They have the ability to change into cells that make up our skin, muscles and brain. Embryonic stem cells are used to test new drugs for safety and effectiveness.

Genes are like tiny instruction manuals that exist inside our cells. They determine many of our traits, like our eye color, height, and also some aspects of our personality. Genes are made up of segments of DNA. DNA carries the genetic information that gets passed on from our parents to us. Each gene carries the specific information needed to produce a particular protein. That particular protein plays a vital role in the structure and functioning of our cells and body.

Mutation refers to a change or alteration in the DNA sequence of a gene. Mutations can occur naturally or be induced by external factors. External factors can be exposure to radiation, particular chemicals, or errors that happen during DNA replication. Mutation can result in loss or replacement of a part of DNA. This can result in altered behaviour of the body cells.

You might have heard about the term cancer. We know that it is a very harmful disease. But have you ever wondered what exactly cancer is? What causes cancer? Cancer is an uncontrolled division of cells in our body. We have already studied that a cell can undergo mitosis in a controlled manner. But in cancer, cells undergo mitosis continuously without any control. The division of cells does not stop.

But why do cells divide in uncontrolled manner in cancer? This is due to mutation in the genes that are involved in cell cycle regulation. Or we can say, alteration in the gene that is responsible for the division of cells causes cancer. The gene that undergoes mutation is called oncogene. This mutation leads to uncontrollable division of cells.

What causes the mutation to genes that are involved in cell cycle regulation? This mutation happens due to carcinogens. Carcinogens are substances or agents that have the potential to cause cancer. They cause the mutation in gene. Tobacco smoke contains numerous carcinogens, including nicotine, tar, and various chemicals such as benzene and formaldehyde. If inhaled, it can higher the risk of cancer. Ultraviolet radiations can also cause cancer.

The uncontrolled division of cells result in the formation of tumor. A tumor is an abnormal mass or lump that forms when cells divide and multiply uncontrollably. There are two types of tumors. These are Malignant tumor and Benign tumor.

A Malignant tumor is a tumor that have the ability to invade nearby tissues. They spread to other parts of the body. These tumors invade nearby tissues by destroying normal tissue structures. Malignant tumor can also break off from original tumor and spread to other parts of the body. They grow at faster rate. They are also called cancerous tumors.

A Benign tumor is a non cancerous growth that develops from abnormal cells in the body. Benign tumors grow in a specific area of the body. They do not invade nearby tissues. Benign tumors typically grow at a slow rate. They are often surrounded by a fibrous capsule that separates them from the surrounding normal tissues.

Metastasis is the process by which cancer cells spread from the original tumor to other parts of the body. During metastasis, cancer cells break away from the primary tumor. After that they invade the nearby blood vessel. This process is called intravasation. After intravasation they travel through blood to distant tissues. After reaching distant tissues, cancer cells exit the blood vessel to enter tissues. This process is called extravasation. After this the cancer cells start to establish secondary tumors in the new location. These secondary tumors are known as metastatic tumors or metastasis.