Meiosis is essential for maintaining the chromosome number in sexually reproducing organisms across generations. Although it reduces the chromosome number by half, fertilization restores it, ensuring genetic stability. Additionally, meiosis introduces genetic variability through crossing over and independent assortment, leading to unique genetic combinations. These variations are crucial for evolution, as they enhance adaptability and...
Overview Meiosis II is initiated immediately after cytokinesis of Meiosis I. It resembles mitosis in its process. Results in the formation of four haploid daughter cells. Phases of Meiosis II 1. Prophase II: Begins immediately after cytokinesis, often before chromosomes fully elongate. Chromosomes become compact again. Nuclear membrane disappears...
Cytokinesis I is the final step of Meiosis I, where the cytoplasm divides, forming two haploid daughter cells. In animal cells, a cleavage furrow develops, which deepens and splits the cell into two. In plant cells, a cell plate forms at the center and extends outward to separate the two new cells. This process ensures that each daughter...
Definition: Minute, membrane-bound vesicles found in both plant and animal cells. Contain various enzymes necessary for cellular processes. Characteristics: Enclosed by a single membrane. Small in size, making them microscopic and distinct. Functions: Facilitate specialized metabolic reactions due to their enzyme content. Play roles in processes like: Detoxification of...
Discovery: First described by Robert Brown in 1831. The material in the nucleus stained by basic dyes was named chromatin by Flemming. Structure of Nucleus Interphase Nucleus: Components: Chromatin: Highly extended nucleoprotein fibers. Nuclear Matrix: Gel-like substance within the nucleus. Nucleoli: Spherical bodies involved in RNA synthesis. Nuclear Envelope:...
Centrosome: An organelle usually containing two cylindrical structures called centrioles. Surrounded by amorphous pericentriolar material. Plays a key role in cell division by forming the spindle apparatus in animal cells. Centrioles: Two centrioles in a centrosome are positioned perpendicular to each other. Structural organization resembles a cartwheel. Composed of:...
Definition & Structure: Hair-like outgrowths of the cell membrane. Two types: Cilia: Small structures. Function like oars to move the cell or the surrounding fluid. Flagella: Longer structures. Primarily responsible for cell movement. Prokaryotic Flagella: Present in bacteria but structurally different from eukaryotic flagella. Ultrastructure: Both cilia and flagella...
Definition: A complex network of filamentous, proteinaceous structures present in the cytoplasm. Composed of microtubules, microfilaments, and intermediate filaments. Components: Microtubules: Hollow, tube-like structures made of tubulin proteins. Microfilaments: Thin, thread-like filaments primarily composed of actin proteins. Intermediate Filaments: Intermediate-sized filaments providing tensile strength and structural support. Functions: Mechanical...
Discovery: Observed as dense particles under an electron microscope by George Palade in 1953. Granular structures composed of ribonucleic acid (RNA) and proteins. Not surrounded by any membrane. Classification: Eukaryotic Ribosomes: Size: 80S. Composed of two subunits: Larger subunit: 60S. Smaller subunit: 40S. Prokaryotic Ribosomes: Size: 70S. Composed of...