Cell Cycle and Mitosis PDF

ARRANGE ME IF YOU CAN!! LECL VIDIOINS CELL DIVISION ARRANGE ME IF YOU CAN!! SOSIMTI MITOSIS ARRANGE ME IF YOU CAN!! PSHAINTREE INTERPHASE ARRANGE ME IF YOU CAN!! ROOOMECHEM CHROMOSOME  Genes orchestrate our physiology from a few days after conception th...

ARRANGE ME IF YOU CAN!! LECL VIDIOINS CELL DIVISION ARRANGE ME IF YOU CAN!! SOSIMTI MITOSIS ARRANGE ME IF YOU CAN!! PSHAINTREE INTERPHASE ARRANGE ME IF YOU CAN!! ROOOMECHEM CHROMOSOME  Genes orchestrate our physiology from a few days after conception through Adulthood. The first cell that leads to the development of a new individual forms when a sperm from a male and an oocyte (also known as egg) from a female join.  CELL DIVISION Allows an increase in cell number or the multiplication of a cell thus, cell division is also cell multiplication Cell Division  Why do cells divide? All organisms need to produce genetically identical daughter cells. Single celled organisms use this method to reproduce - each of the produced cells is a separate organism. For multicellular organisms, there are three main reasons why cells divide: ❑Growth - multicellular organisms can grow in two ways, increasing the size of their cells, or increasing the number of cells - achieved through mitosis. ❑Repair - when cells are damaged, they need to be replaced with identical cells capable of doing exactly the same job. ❑Replacement - no cell lasts forever. Even the most long lived of cells will need to be replaced at some point. Red blood cells only last three months, skin cells even less. Identical cells are needed to carry on the functions of the cells they are replacing.  Cell Cycle The cell cycle can be thought of as the life cycle of a cell. In other words, it is the series of growth and development steps a cell undergoes between its “birth”—formation by the division of a mother cell—and reproduction—division to make two new daughter cells.  Stages of the cell cycle To divide, a cell must complete several important tasks: it must grow copy its genetic material (DNA) physically split into two daughter cells Cells perform these tasks in an organized, predictable series of steps that make up the cell cycle. The cell cycle is a cycle, rather than a linear pathway, because at the end of each go-round, the two daughter cells can start the exact same process over again from the beginning.  Stages of the cell cycle In eukaryotic cells, or cells with a nucleus, the stages of the cell cycle are divided into two major phases: interphase and the mitotic (M) phase. During interphase, the cell grows and makes a copy of its DNA. During the mitotic (M) phase, the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells.  INTERPHASE ❑G1 PHASE ❑ S PHASE ❑G2 PHASE  G1 PHASE ❑During G1, also called the first gap phase, the cell grows physically larger, copies organelles, and makes the molecular building blocks it will need in later steps. ❑The cell synthesizes mRNA and proteins, which is are needed for chromosome replication ❑There are two checkpoints in G1, the G1 damage checkpoint and the restriction check point  G1 DNA CHECKPOINT ❑Evaluates the DNA’s integrity ❑Damaged DNA results in the accumulation of p53 proteins that can trigger either cell cycle arrest apoptosis. ❑The p53 proteins(also called TP53) are tumor- suppressing proteins that helps regulating the cell cycle  APOPTOSIS ❑Comes from the Ancient Greek word Apo which means away and tosis meaning falling. ❑The cells between your embryonic fingers died in a process called apoptosis, a common form of programmed cell death. ❑In programmed cell death, cells undergo “cellular suicide” when they receive certain cues.  RESTRICTION CHECKPOINT ❑ Evaluates the cell’s capability yo undergo cell division. ❑If the cell is ready it will proceed to S phase. If not, G0. ❑Cells in G0 are either quiescent (dormant) or senescent (aging or deteriorating)  S PHASE ❑ S (SYNTHESIS) phase, chromosome are replicated. ❑This means is twice the actual DNA now present in the cell. ❑Each of the chromosomes consists of two chromatids. ❑Chromatids- is one copy of a newly copied chromosome.  S PHASE ❑ in S phase the chromosome is not visible and will become visible only in the prophase. ❑S DNA DAMAGE CHECKPOINT monitors the replication process in this phase.  G2 PHASE ❑ At this point, the cell rapidly grows and protein synthesis continues. ❑G2 DNA DAMAGE CHECKPOINT- Checks activities in G2 to ensure its proper flow. ❑UNREPLICATED DNA CHECKPOINT ensures that DNA synthesis is complete before proceeding to mitosis.  Mitosis is division of the nucleus into two genetically identical daughter nuclei. Get the terminology right centrioles organize spindle microtubules centromere is the part of a chromosome that Spindle links sister chromatids microtubules (also referred to as spindle fibres) In animal cells two centrioles are held by a protein mass referred to as a centrosome Sister chromatids are duplicated It is easy to misuse the terms chromatid and chromosomes attached by a centromere chromosome. It is even easier to confuse the terms centromere, centriole and centrosome due to their After anaphase when the sister chromatids similar spelling. Keep the terms clear in your mind separate they should then be referred to as to avoid losing marks. chromosomes ❑ it ensures that the number of chromosomes of parent cell is identical to two daughter cell. ❑For example, humans have 46 chromosomes in each cell in the diploid state 2(n). ❑A diploid cell has two sets of chromosomes, each coming from parent cell. ❑ it replaces the damage cells in wound ❑While the mitosis gives benefits to the body, it can also cause problems. ❖Located in chromosome 17 are p53. ❑The growth of our hair also due to mitotic activity of its root.  DNA supercoils* chromatin condenses and becomes sister chromatids, which are visible under a light microscope The kinetochore – a special protein complex, appears at The centrosomes the centromere. The move to opposite function of poles of the cell and kinetochore is to link spindle fibers begin to form between the spindle fibers to them centromere The nuclear membrane is broken down and disappears  METAPHASE ❑In this phase, there are three kinds of microtubules in the spindle fibers ASTRAL POLAR KINETECHORE  ASTRAL MICROTUBULES ❑ are those that grow only near the centrosome (the structure with the centrioles)  POLAR MICROTUBULES ❑ Grow away the centrosome. These overlap at the middle where the chromosome are located, but they are not still attached to the kinetochore. KINETOCHORE MICROTUBULES ❑ are those only attached to the KINETOCHORE  Metaphase Plate or Equatorial Plate Spindle fibers from each of the two centrosomes attach to the centromere of each pair of sister chromatids Contraction of the microtubule spindle fibers cause the sister chromatids to line up along the center of the cell.  Spindle Assembly Checkpoint Guarantees the proper alignment of the chromosomes at the metaphase plate  Continued contraction of the microtubule spindle fibres cause the separation of the sister chromatids Chromosomes move to the The chromatids are now opposite poles of the cell referred to as chromosomes CYTOKINESIS STARTS IN THIS PHASE AND CONTINUE IN THE NEXT PHASE  ANAPHASE ❑There are two substages in anaphase, namely: ✓Anaphase A ✓Anaphase B ❑Plant cells rarely have anaphase B. ❑Sometimes anaphase A happens before anaphase B and vice versa.  The chromosomes uncoil de-condense to chromatin (and are no Chromosomes longer visible under a arrive at the poles. light microscope). Microtubule spindle fibers disappear New nuclear membranes reform around each set of chromosomes