General Biology Lesson 4 PDF

GENERAL BIOLOGY LESSON 4 General Biology 1 Mitosis 2n=6 and Application  Biology is the study of complicated things that have the appearance of having been designed with a purp...

GENERAL BIOLOGY LESSON 4 General Biology 1 Mitosis 2n=6 and Application  Biology is the study of complicated things that have the appearance of having been designed with a purpose. Defining Biology Richard Dawkins Introduction General Biology 1 Cell division is a very important process in all living organisms. During the division of a cell, DNA replication and cell growth also take place. All these processes, example cell division, DNA replication, and cell growth, hence, have to take place in a coordinated way to ensure correct division and formation of progeny cells containing intact genomes.  General Biology 1 The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells is termed cell cycle. Although cell growth (in terms of cytoplasmic increase) is a continuous process, DNA synthesis occurs only during one specific stage in the cell cycle. The replicated chromosomes (DNA) are then distributed to daughter nuclei by a complex series of events during cell division.  Biology 1 M is the phase of the cell cycle in which the microtubular apparatus assembles, binds to the chromosomes and moves the sister chromatids apart. Called mitosis, this process is the essential step in the separation of the two daughter genomes. Although mitosis is a continuous process, it is traditionally subdivided into four stages: prophase, metaphase, anaphase, and telophase.  General Biology 1 Cytokinesis The eukaryotic cell has partitioned its replicated genome into two nuclei positioned at opposite ends of the cell. While mitosis was going on, the cytoplasmic organelles, including mitochondria and chloroplasts (if present), were reassorted to areas that will separate and become the daughter cells. The phase of the cell cycle when the cell actually divides is called cytokinesis. It generally involves the cleavage of the cell into roughly equal halves. What is Mitosis? General Biology 1 Mitosis, a process of cell duplication, or reproduction, during which one cell gives rise to two genetically identical daughter cells. The newly formed daughter cells are genetically identical to the parent cell and to each other. Strictly applied, the term mitosis is used to describe the duplication and distribution of chromosomes, the structures that carry the genetic information. During the mitosis process, the cell’s nucleus along with the chromosome is divided to form two new daughter cell nuclei. The daughter nuclei inherit the same number of chromosomes as that of the parent nucleus. Mitosis PMAT stages General Biology 1 Prophase Biology 1 Prophase is marked by the initiation of condensation of chromosomal material. The chromosomal material becomes untangled during the process of chromatin condensation. The centriole, which had undergone duplication during S phase of interphase, now begins to move towards opposite poles of the cell. The completion of prophase can thus be marked by the following characteristic events: *Chromosomal material condenses to form compact mitotic chromosomes. Chromosomes are seen to be composed of two chromatids attached together at the centromere. * Initiation of the assembly of mitotic spindle, the microtubules, the proteinaceous components of the cell Metaphase Biology 1 The complete disintegration of the nuclear envelope marks the start of the second phase of mitosis; hence the chromosomes are spread through the cytoplasm of the cell. The key features of metaphase are: *Spindle fibers attach to kinetochores of chromosomes. *Chromosomes are moved to spindle equator and get aligned along metaphase plate through spindle fibres to both poles.  Biology 1 Anaphase At the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids, now referred to as chromosomes of the future daughter nuclei, begin their migration towards the two opposite poles. Key events: *Centromeres split and chromatids separate. *Chromatids move to opposite poles. Telophase Biology 1 the chromosomes that have reached their respective poles decondense and lose their individuality. The individual chromosomes can no longer be seen and chromatin material tends to collect in a mass in the two poles. This is the stage which shows the following key events: *Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. * Nuclear envelope assembles around the chromosome clusters. * Nucleolus, Golgi complex and ER reform.  Biology 1 Mitosis helps in the splitting of chromosomes during cell division and generates two new daughter cells. Therefore, the chromosomes form from the parent chromosomes by copying the exact DNA. Therefore, the daughter cells formed as genetically uniform and identical to the parent as well as to each other. Thus, mitosis helps in preserving and maintaining the genetic stability of a particular population.  Criteria: Content - (15 Points) Organization - (10 Points) Neatness - (5 Points) No usage of AI Tools, write it in your own words NEXT LESSON General Biology 1 Meiosis