Abnormalities of Cell Division & Cell Cycle PDF

updated 08 /09 / 2023. ABNORMALITIES IN CELL DIVISION Nondisjunction of chromosomes or chromatids means failure of separation migration of one or more chromosomes or chromatids to one pole of the dividing cell. Thus, one daughter cell receives...

updated 08 /09 / 2023. ABNORMALITIES IN CELL DIVISION Nondisjunction of chromosomes or chromatids means failure of separation migration of one or more chromosomes or chromatids to one pole of the dividing cell. Thus, one daughter cell receives one or more extra chromosomes while the other cell doesn’t receive any of them. Mis-division at the centromere (formation of isochromosomes): means abnormal transverse division of the chromosome instead of longitudinal division. The resulting chromosomes: one has four short arms and the second has four long arms. The ends of these resulted chromosomes are sticky, so the ends join each other forming ring chromosome. The Life Cycle of the Cell The somatic cells start their life as daughter cells after mitotic cell division of the mother cell. Then, they perform their specific functions till they divide once again. The Cell Cycle is the changes that occur in the cell during its cell division (mitosis) and rest (inter phase). The cell cycle is divided into mitotic period and Inter-phase: 1. The Mitotic period is the time of cell division during which each cell divides into two identical daughter cells. 2. The inter-phase is the time during which the cell is performing its functions before starting another cell division. This inter-phase is subdivided into four stages: G0, G1, S and G2 stages. G0 Stage: if the cell leaves the cycle during G0, it re- enters the cycle once again. G1 Stage (Gap One stage): This is the period between the end of mitosis and the beginning of the next S – stage. In this stage, the nucleus of each daughter cell has 46 1 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License updated 08 /09 / 2023. chromatids which are called inter-phase chromosomes (S- chromosomes). Some cells may leave the cell cycle during this stage forever to perform their specialized functions; these cells called End Cells. No further division of end cells during their life. During G1, the cell forms its own proteins. S-Stage (Synthesis Stage): It follows G1-Stage. During stage, the cell duplicates its amount of DNA. Each cell has 92 S- chromosomes. G2 Stage (gap two-Stage): It is a very short period. It lies between S-Stage and the beginning of the next mitosis. *During G2 stage, each identical pair of chromatids joins together at the centromere to form d- chromosome for the next mitosis (d from double chromatids). *The number of centrioles is duplicated. *The amount of tubulin protein has increased. Thus, the cell in G2-Stage contains 46 pairs of identical chromatids (d- chromosomes) and 4 centrioles. 2 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License updated 08 /09 / 2023. Clinical Relevance: cancer cell division Antimitotic drugs Summaries and Key Points: cell cycle References and Additional Resources: Basic Histology by Jane Quire Latest Edition Color Atlas of Histology by Lesie P Gartner Latest Edition NAME: Nadia Mahmoud DESIGNATION: prof. of Histology DEPARTMENT: biomedical sciences 3 DUBAI MEDICAL COLLEGE FOR GIRLS (DMCG), 2023. ©2023 by DMCG. This work is licensed under a Creative Commons Attribution-Non Commercial-Share Alike 4.0 International License