Detailed Study Notes on Cell Division and Information Flow

Key Concepts of Cellular Division and Information Flow

The study focuses on information flow in biological systems, particularly through cellular division which includes complex processes such as mitosis.
It is noted that DNA (composed of bases adenine [A], guanine [G], cytosine [C], and thymine [T]) is transcribed to messenger RNA (mRNA), which is then translated into proteins essential for biological functions.
The lecture emphasizes understanding how these components interact at a molecular level to facilitate processes of life.

Mitosis is defined as cellular division that results in two genetically identical daughter cells from a single mother cell, emphasizing that these cells maintain the same genome.
Important point: While mitosis aims for genetic identity, variations can occur, leading to different cell types within an organism.
Example: All cells in a multicellular organism like humans are genetically identical, yet they perform distinct functions based on gene expression.

Binary Fission: Found in prokaryotes (e.g., bacteria), is a simpler form of division compared to mitosis.
Eukaryotic Cell Cycle: More complex than binary fission and consists of several phases leading to mitotic division.

The cell cycle is the process through which a cell goes from one division to another, largely consisting of two main phases: Interphase (cell growth and preparation) and Mitotic Phase (actual cell division).
Key phases of the cell cycle include:
- G1 Phase (Gap 1): Cell growth and preparation to divide.
- S Phase (Synthesis): Wide range of resources is devoted to replicating the cell's genome.
- G2 Phase (Gap 2): Further growth, organelle replication, and preparation for mitosis.
- M Phase (Mitosis): The phase during which cell division occurs.

The G0 Phase: Describes non-dividing cell states where cells are not actively dividing but carrying out other functions (e.g., heart cells).

DNA exists in an uncondensed form known as chromatin during interphase.
During mitosis, chromatin condenses to form chromosomes, which consist of two sister chromatids connected at a region called the centromere.
Karyotype: An organized representation of chromosomes at metaphase, useful for studying genetic information.

Chromosomes are typically represented as X-shaped structures consisting of two identical copies (sister chromatids).
Telomeres: The ends of chromosomes that protect genetic data during cell division.
Diploids: Organism has two copies of each chromosome (e.g., humans have 46 chromosomes, arranged in homologous pairs).

Prophase: Chromosomes condense and become visible; the nuclear envelope remains intact.
Prometaphase: Breakdown of the nuclear envelope, chromosomes fully condense, and microtubules attach to kinetochores.
Metaphase: Chromosomes align on the metaphase plate, organized by microtubules.
Anaphase: Sister chromatids separate and are pulled towards opposite poles of the cell.
Telophase: Nuclear envelope starts to reform around each set of chromosomes; the final preparation for division begins.
Cytokinesis: Division of the cytoplasm, different in plant and animal cells.

In animal cells, cytokinesis is achieved through the formation of a cleavage furrow which bisects the cell.

Plant cells form a phragmoplast instead of a cleavage furrow, constructing a new cell wall.

Fungal cells can bud off, showing alternative methods of asexual reproduction while maintaining genetic material.

Mitosis ensures genetic continuity in asexual reproduction in bacteria and multicellular organisms.
Each phase of the cell cycle is critical for the accurate division of cellular components ensuring successful cell replication.
Understanding the cellular and molecular basis of mitosis is essential for comprehending broader biological processes such as growth, development, and reproduction in organisms.