Cell Cycle: Flow Cytometry, Interphase, and Cell Division
Flow Cytometry
Interface: G1 – S – G2
When the cell is not in cell division, it is in interphase:
- G1 – State: Initiation of the cell’s life cycle.
- S – Synthesis of DNA, DNA duplication.
- G2 – The cell enters a resting state.
Interphasic Nucleus
Organelle characteristic of eukaryotic cells.
- Form: Ovoidal
- Location: In animal cells, it is at the center; in plant cells, it is on the side.
- Size: Approximately 5 microns in animal cells.
- Number: 1 nucleus in animal and plant cells; 2 nuclei in fungi. There are also cells without a nucleus (anucleated), such as mature red blood cells. Some muscle fibers are multinucleated.
Nucleolemma
Separates the nuclear membrane from the cytoplasm inside the nucleus.
- Double membrane: Phospholipids and proteins (fluid mosaic)
- Formation of a lattice-based structure. Reticulum.
- Pore structures: Regulation and transport of substances.
Nucleoplasm
- Water-based with different ions
- Nutrients
- Nucleotides, the building blocks of nucleic acids.
Nucleolus
- Involved in ribosome manufacturing.
Chromatin
- High affinity for dyes
- Composed of DNA and proteins
- In interphase, DNA and proteins form fibers called 100 Angstrom fibers or ‘necklace of pearls’.
- The physical location where genetic information is stored.
Cell Division
- Renewal (mitosis) – Creation of new somatic cells.
- Reproduction (meiosis) – Cells reproduce.
Genetic information doubles before mitosis. At the beginning of mitosis, chromatin condenses and forms chromosomes.
Somatic Cells
- Diploid (2n) – 46 chromosomes (23 pairs)
- One set of chromosomes comes from each parent.
Gametes
- Haploid (n) – 23 chromosomes (not paired)
- Young: 1, 2, 3, … 23.
Mitosis
The process by which a diploid cell produces two diploid cells.
In a diploid cell, homologous chromosomes are pairs (e.g., 1.1). These pairs are identical, except for those that determine sex.
Chromosomes that determine sex are called heterochromosomes, while the others are called autosomes.
Mitosis Stages
Prophase: Duplication of centrioles. The nucleus increases in size. Chromatin begins to condense. Centrioles migrate to opposite poles. The achromatic spindle begins to form. Chromosomes become visible. The nuclear membrane begins to disappear. The achromatic spindle is completed. Chromosomes attach to the spindle fibers and move to the cell’s equator.
Metaphase: Chromosomes align at the cell’s equator.
Anaphase: Sister chromatids separate and move towards opposite poles.
Telophase: Condensed chromosomes begin to decondense. The achromatic spindle disappears. The nuclear membrane begins to reform. Vesicles accumulate at the cell’s equator.
Cytokinesis: In animal cells, the cell divides. In plant cells, a cell plate (phragmoplast) forms to separate the cells.
Meiosis
The process of cell division by which a diploid cell produces four haploid cells.
Occurs only in organisms that produce reproductive gametes.
Meiosis I
Prophase I: Divided into five sub-phases:
- Leptotene: Homologous chromosomes begin to pair.
- Zygotene: Homologous chromosomes align closely.
- Pachytene: Homologous chromosomes come into physical contact, and crossing over (recombination) occurs.
- Diplotene: Homologous chromosomes begin to separate, and chiasmata (points of crossing over) become visible.
- Diakinesis: The final stage of prophase I.
Metaphase I: Homologous chromosomes align at the cell’s equator.
Anaphase I: Homologous chromosomes separate and move to opposite poles.
Telophase I: Chromosomes reach the poles, and cytokinesis occurs (one diploid cell becomes two haploid cells).
Meiosis II
Prophase II is similar to mitosis. Metaphase II is similar to mitosis. Anaphase II is similar to mitosis. Telophase II is similar to mitosis.