2.6 Cell cycle, Cell division, differentiation

• The cell cycle consists of interphase (G1 phase, S phase, G2 phase) and mitosis.
• Interphase is the longest part of the cell cycle and involves DNA replication during the S phase.
• Mitosis is the process by which cells divide to produce two daughter cells with identical chromosome numbers.
• Cytokinesis occurs at the end of mitosis when the cytoplasm divides into two new cells.
• Meiosis produces four genetically diverse haploid gametes from one diploid parental cell.
• Cell division can be used for growth or repair purposes.
• During mitosis, sister chromatids separate at anaphase, resulting in two identical sets of chromosomes in each daughter nucleus.
• Stem cells are undifferentiated cells that can develop into specialized cells through differentiation.
• Cell division allows organisms to grow, repair damaged tissues, replace old or worn-out cells, and reproduce sexually.
• Different types of stem cells have specific functions such as embryonic stem cells that are pluripotent and adult stem cells that are multipotent.
• The G1 checkpoint ensures that all necessary preparations have been made for DNA synthesis.
• The G2 checkpoint checks whether there are any errors in DNA replication and if the cell has enough energy reserves for cytokinesis.
• In interphase, the cell grows and prepares for DNA replication.
• Embryonic stem cells have the potential to become any type of cell in the body.
• Tissue-specific stem cells are found within adult tissue and can generate more cells of the same type.
• Cell division has two main stages: interphase and the mitotic or M phase.
• During interphase, each chromosome is copied to form two sister chromatids and the sister chromatids remain joined at the centromere.
• During interphase, the chromosomes are not visible as distinct structures in the nucleus of the cell.
• The stages of mitosis are prophase, metaphase, anaphase, and telophase.
• During prophase, the chromosomes condense and become visible in the nucleus, each chromosome consists of two sister chromatids joined at the centromere, the nucleolus disappears and the nuclear membrane starts to break down, a pair of centrioles move to either side pole of the cell, proteins begin to form spindle fibers which attach to the centromere of each chromosome, and these spindle fibers start to move the chromosomes towards the center of the cell.
• During metaphase, the spindle apparatus has completely formed and the chromosomes are lined up at the center or equator of the cell.
• During anaphase, the centromeres divide into two and the spindle fibers begin to shorten, pulling the sister chromatids towards opposite poles of the cell.
• During telophase, the chromatids have reached the pole of the cell and scientists now refer to them as chromosomes, the spindle operators breaks down and the nuclear membranes reform, the chromosomes uncoil back to their chromatin state and the nucleolus reappears in each nucleus.
• The cell has now finished nuclear division by mitosis and starts cytokinesis, during cytokinesis the central cell membrane is pulled inwards by the cytoskeleton, creating a groove or furrow which gradually deepens and eventually the membranes fuse to form two independent cells.
• The cell cycle is the regulated sequence of events that occurs between one cell division and the next
• The cell cycle has three phases: interphase, nuclear division (mitosis), and cell division (cytokinesis)
• The length of the cell cycle varies depending on environmental conditions, cell type, and organism
• Chemical signals called cyclins trigger the movement from one phase to another in the cell cycle
• Interphase consists of three phases: G phase, S phase, and G phase
• During the G phase, the cell receives a signal to divide again
• DNA in the nucleus replicates during the S phase, resulting in each chromosome consisting of two identical sister chromatids
• The G phase occurs between the S phase and the next cell division event, where the cell continues to grow and prepares for cell division
• Nuclear division (mitosis) follows interphase
• Mitosis is the process of nuclear division by which two genetically identical daughter nuclei are produced
• Mitosis can be divided into four main stages: Prophase, Metaphase, Anaphase, and Telophase
• During Prophase, chromosomes condense, centrosomes move towards opposite poles, and the nuclear envelope breaks down
• During Metaphase, chromosomes line up at the equator of the spindle and spindle fibers attach to the centromeres
• During Anaphase, sister chromatids separate at the centromere and are pulled to opposite poles by the spindle fibers
• During Telophase, chromosomes arrive at opposite poles, nuclear envelopes begin to reform, and new nucleoli form within each nucleus
• Flow cytometry can be used to measure the mass of DNA in a sample of cells throughout a cell cycle