<span>Cells control cell division in order to maintain normal cell function. If something happens to the control of the cell division, the healthy cells will divide uncontrollably. These new cells are cancer cells. </span>
The mutations in three genes are responsible for development of cancers:
1. Mutation in proto-oncogenes. Proto-oncogenes normally signal cells to grow and differentiate. Proto-oncogenes can become oncogenes due to mutations which result in the uncontrollable division of the cells.
2. Mutation in tumor suppressor genes. In normal cells, tumor suppressor genes suppress genes essential for cell cycle and that way they prevent uncontrollable cell division. However, after a mutation in these genes, suppression is lost and the cell may progress to cancer.
3. Mutation in stability genes. In normal cells, they have no role either in cell death or growth, but they control mutation rate. Mutation in stability genes results in situation where all genes, including proto-oncogenes and tumor suppression genes, are more frequently mutated.
T killer cell or Cytotoxic T cells are the cells in animals that are used to destroy bacteria and viruses after combining with lysosomes.
<u>Explanation</u>:
The T cells kills the bacteria and virus. The T cells can easily identify the pathogen when combined with the lysosomes. The activated T cells releases a material called perforin. This substance gets into the walls of the affected cell and punctures its walls. Due to hole in the walls, there happens discharge of fluid and electrolytes, which leads to the death of the cell. The substance secreted is the cytolytic proteins from the lysosome which helps in destruction of the infected cells.
Answer:
John S. ... “It was stated above that traditional archaeology is concerned with the reconstruction of ancient cultural systems while the 'new archaeologist' looks for explanations of cultural change that can be used to predict particular changes in particular situations” (Justeson 131).
I believe it is called <span>hair density.
I hope this helps!</span>
