Cell and Cell Division

Many chloroplast DNAs contain two inverted repeats, which separate a long single copy section (LSC) from a short single copy section (SSC). While a given pair of inverted repeats is rarely completely identical, they are always very similar to each other, apparently resulting from concerted evolution.

The chromosomes continue to become denser. The homologous pairs have also found each other and begin to initially align with one another, referred to as 'rough pairing'. Lateral elements also form between the two homologous pairs, forming a synaptonemal complex.

The protein-rich alkaline aqueous fluid within the inner chloroplast membrane and outside of the thylakoid space is called the stroma, which corresponds to the cytosol of the original cyanobacterium.  

Nucleus is a site for transcription in which messenger RNA (mRNA) are produced for protein synthesis.

During this stage, the centromeres that contain two kinetochores attach to the spindle fibers at each pole from the centrioles. The equatorial plate formed here is rotated by 90 degrees, compared to meiosis I and is perpendicular to the previous metaphase plate.

The protein molecules in the cell membrane receive signals from other cells or the outside environment and convert the signals to messages that are passed to the organelles inside the cell.

Also known as the monarchial type of chromosomes, they have a centromere that is located towards the end of the chromosome. Thus, telocentric chromosomes have a 'rod' shaped appearance. In some cases, the telomeres extend from both the chromosome ends. The telocentric chromosome is not present in humans.

They are the jelly types of organelles, which are present in the inner region of a cell. It plays a vital role in keeping a cell in a stable and keeps the cell organelles separate from each other.

The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation.

Acentric chromosomes are those that lack centromeres, i.e. the centromere is totally absent on the chromosome. These chromosomes are observed due to effects of chromosome-breaking process like irradiation.

A contractile ring made of non-muscle myosin II and actin filaments assembles equatorially (in the middle of the cell) at the cell cortex (adjacent to the cell membrane). Myosin II uses the free energy released when ATP is hydrolysed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow.

Tannosomes are organelles found in plant cells of vascular plants. Tannosomes are formed when chloroplast membrane form pockets filled with tannin. Slowly, the pockets break off as tiny vacuoles that carry tannin and went toward the large vacuole filled with acidic fluid. Tannin are then released into the vacuole and stored inside as tannin accretions.

Meiosis begins with one diploid cell containing two copies of each chromosome- one from the organism's mother and one from its father. The cell divides twice, potentially producing up to four haploid cells containing one copy of each chromosome.

Microfilaments are the thinnest filaments of the cytoskeleton, a structure found in the cytoplasm of eukaryotic cells. These linear polymers of actin subunits are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton tensile forces.  

The smooth endoplasmic reticulum serves many general functions, including the folding of protein molecules in sacs called cisternae and the transport of synthesized proteins in vesicles to the Golgi apparatus.