Cell and nuclear division

• In all living organisms, a parent cell divides to produce two daughter cells
• Cytokinesis in animal cells involves a ring of contractile actin and myosin proteins pinching the cell membrane together to split the cytoplasm
• Cytokinesis in plant cells involves vesicles assembling sections of membrane and cell wall to achieve splitting
• Equal cytokinesis is when division of cytoplasm is usually equal, ensuring both daughter cells receive at least one mitochondrion and any organelle that can only be made by dividing a pre-existing structure
• Unequal cytokinesis examples include oogenesis in humans and budding in yeast
• Mitosis maintains chromosome number and genome of cells, while meiosis halves the chromosome number and generates genetic diversity
• DNA replication is a prerequisite for both mitosis and meiosis, resulting in each chromosome consisting of two elongated DNA molecules (chromatids)
• Histones play a role in condensing DNA by supercoiling in mitosis and meiosis
• Microtubules and microtubule motors are used to move chromosomes in mitosis and meiosis
• Mitosis consists of four main stages: Prophase, Metaphase, Anaphase, Telophase
• Interphase is the stage between two cell divisions, consisting of G1 phase, S phase, and G2 phase
• Chromatin is loosely packed DNA in non-dividing cells, while chromosomes are organized DNA during mitosis
• The cell cycle includes interphase and mitosis, with interphase being the longest and most active phase
• Meiosis is a reduction division, producing four haploid nuclei from one diploid nucleus
• Meiosis is necessary in a sexual life cycle and involves two rounds of segregation
• Down syndrome is an example of an error in meiosis known as non-disjunction
• Meiosis generates genetic diversity through random orientation of bivalents and crossing over
• Nuclear division must occur before cell division to avoid producing anucleate cells
• Mitosis and meiosis are two types of cell division, with mitosis maintaining chromosome number and genome, while meiosis halves the chromosome number and generates genetic diversity
• Mitosis produces daughter cells with the same number of chromosomes as the parent cell, known as the diploid state
• Meiosis produces daughter cells with half the number of chromosomes of the parent cell, known as the haploid state
• Mitosis occurs during growth, cell replacement, and asexual reproduction, while meiosis occurs during gamete formation
• The cell cycle is the regulated sequence of events between cell divisions, consisting of interphase and mitosis
• Interphase includes G1 phase for growth, S phase for DNA synthesis, and G2 phase for cell growth and preparation for division
• Mitosis is preceded by interphase and divided into Prophase, Metaphase, Anaphase, and Telophase
• During Prophase, DNA supercoils, chromosomes condense, and centrosomes move to opposite poles of the cell
• During Metaphase, sister chromatids line up at the equator of the cell and spindle fibers attach to centromeres
• During Anaphase, sister chromatids separate at the centromere and are pulled to opposite poles by spindle fibers
• During Telophase, chromosomes decondense, nuclear envelopes form, and cytokinesis splits the cell into two daughter cells
• Cytokinesis in animal cells involves a cleavage furrow formed by microtubule filaments, while in plant cells, vesicles form a cell plate to divide the cell
• Equal cytokinesis ensures both daughter cells receive necessary organelles, while unequal cytokinesis results in uneven division such as in oogenesis and budding in yeast