Meiosis is a crucial process in eukaryotic cells involving two distinct divisions that reduce the chromosome number by half, resulting in four genetically diverse cells. This process includes various phases such as Prophase, Metaphase, Anaphase, and Telophase, each contributing to the accurate segregation of chromosomes.
G2 Interphase:
The chromosomes have two chromatids each.
The drawing shows two cells. Each cell has 8 chromosomes. Each chromosome has 2 chromatids for a total of 16 chromatids per cell.
G1 Interphase:
The chromosomes have 1 chromatid.
Two cells each cell has 8 chromosomes. Each chromosome has 1 chromatid for a total of 8 chromatids per cell.
Telophase:
The cell divides into two.
The chromosomes uncoil.
The nucleus reforms.
The spindle apparatus disassembles.
Anaphase:
The chromatids separate, the number of chromosomes doubles.
A cell with 16 chromosomes. Each chromosome has 1 chromatid total is 16 chromatids
Metaphase:
The chromosomes become aligned.
Prophase:
-The chromosomes coil.
-The nuclear membrane disintegrates.
-Spindle fibers (microtubules) form.
A cell with 8 chromosomes. Each chromosome has 2 chromatids for a total 16 chromatids.
Interphase:
Chromosomes not visible because they are uncoiled
STRUCTURES
Organelles
Functions: an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer.
Ribosomes
Functions: site of protein synthesis (translation).
Found in all eukaryotic and prokaryotic cells.
Cytoplasm
Functions: A complex network of thread jelly-like and tube-like structures, which provides support, shape, and movement.
-Microfilaments
-Intermediate filaments
-Microtubules
Cell membrane
Functions: Contain carbohydrates for cell recognition and serve as sites for bacterial attachment.
Contain sterols which increase resistance to osmotic lysis.
Flagella and Cilia
Functions: for locomotion and movement substances along cell surface.
MEIOSIS
Phases in Meiosis II – SIMILAR TO MITOSIS
The second meiotic division is like mitosis, the number of chromosomes does not get reduce (still 4 but single chromatid. As in mitosis, pairs of chromatids will form later)
PHASES
Telophase I:
-The nuclear envelope reforms
-Two cells formed
-Each cell is N with 4 chromosomes
-In the first meiotic division, the number of cells is doubled (one cell to two cells) and the number of chromosomes is reduced by half (8 to 4 with 8 chromatids)
Anaphase I:
Separation of homologous chromosome
Metaphase I:
-Bivalents (tetrads) aligned in the center of cell and attached to spindle fibers.
-The chromosome alignment illustrated from a cell with a diploid chromosome number of 8.
Prophase I:
-Events similar to prophase of mitosis. The chromosomes coil up, the nuclear membrane disintegrate, and centrosomes moving apart.
-Synapsis (joining) of homologous chromosomes produce tetrads.
-The two chromosomes may exchange fragments by a process called crossing over.
ORGANELLES
Others organelles
Centriole - Function: Help to organize the assembly of microtubules during cell division.
Chromoplast - Function: Synthesize and store pigments.
Function: site of cellular respiration, produces ATP
Chloroplasts
Function: captures sunlight for
photosynthesis.
Vacuoles
Functions:
-Central vacuole: In plant cells. Store starch, water, pigments, poisons, and wastes.
-Contractile vacuole: Regulate water balance, by removing excess water from cell.
-Food or Digestion Vacuole: Engulf nutrients in many protozoa (protists).
Lysosomes
Functions:
-Molecular garbage dump and recycler of macromolecules
-Destruction of foreign material
-Digestion of food particles taken in by cell.
Golgi Apparatus
Function: protein packaging factory.
Endoplasmic Reticulum (ER)
Smooth ER - Functions:
-Lipid Synthesis
-Breakdown of toxic compounds
-Regulates sugar
-Calcium storage
Rough ER - Functions:
-Synthesis and modification of proteins.
-Synthesis of cell and organelle membranes.
