What tissue covers the outside of the body and lines organs within the body?

Transcription is the process by which an RNA molecule is synthesized from a DNA template. It is a key step in gene expression and occurs in the nucleus of eukaryotic cells (and in the cytoplasm of prokaryotic cells). During transcription, RNA polymerase enzyme binds to a specific region of DNA called the promoter and unwinds the DNA double helix. One of the DNA strands, known as the template strand, serves as a template for RNA synthesis, while the other strand remains untranscribed. RNA polymerase catalyzes the formation of phosphodiester bonds between ribonucleotides, resulting in the synthesis of a complementary RNA molecule. The RNA transcript is synthesized in the 5' to 3' direction and is complementary to the template DNA strand, except that uracil (U) is used in place of thymine (T) in RNA. Transcription terminates when RNA polymerase reaches a sequence called the terminator, causing RNA polymerase to dissociate from the DNA template, and the newly synthesized RNA molecule is released. Transcription produces several types of RNA molecules, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), which play essential roles in protein synthesis and gene regulation.

An isotonic solution is a solution with the same concentration of solutes as the cytoplasm of cells. When cells are placed in an isotonic solution, there is no net movement of water across the cell membrane, and the cells maintain their normal shape and volume. Isotonic solutions are commonly used in medical settings for intravenous (IV) fluid therapy and to prepare medications for injection. Injecting isotonic solutions into tissues or the circulatory system helps prevent cells from experiencing osmotic imbalances that could lead to cell shrinkage (crenation) or swelling (lysis). Examples of isotonic solutions used in medicine include normal saline (0.9% NaCl) and Lactated Ringer's solution, which closely match the osmolarity of bodily fluids and are well-tolerated by cells. Isotonic solutions are also used in laboratory settings for cell culture and to maintain the osmotic balance of cells during experimental procedures. Overall, isotonic solutions play a crucial role in maintaining cellular homeostasis and preventing damage to cells exposed to external fluids or medications.

Homeostasis is the process by which living organisms maintain stable internal conditions despite changes in their external environment. It involves the regulation of various physiological parameters such as temperature, pH, ion concentrations, and nutrient levels within narrow ranges suitable for cellular function. In the human body, for example, homeostatic mechanisms regulate body temperature, blood pressure, blood glucose levels, and pH balance to ensure optimal physiological function. Homeostasis is achieved through feedback loops that involve sensors, control centers, and effectors. Positive feedback loops amplify deviations from the set point, while negative feedback loops counteract deviations by promoting responses that bring the system back to its desired state. Homeostasis is essential for the survival and proper functioning of cells, tissues, organs, and organisms.

Mitosis is a process of nuclear division in eukaryotic cells that ensures each daughter cell receives an identical copy of the parent cell's chromosomes. Mitosis is divided into four main stages: prophase, metaphase, anaphase, and telophase. During prophase, chromatin condenses into visible chromosomes, the nuclear envelope disintegrates, and the mitotic spindle apparatus forms. In metaphase, chromosomes align along the metaphase plate (equatorial plane) of the cell, with spindle fibers attached to the centromeres of each chromosome. In anaphase, sister chromatids are pulled apart toward opposite poles of the cell by spindle fibers, resulting in the segregation of genetic material. Finally, in telophase, the nuclear envelope reforms around the separated chromosomes at each pole, and the spindle apparatus disassembles. Chromatin decondenses, and nucleoli reappear in each daughter nucleus. Cytokinesis, the division of the cytoplasm and organelles, typically occurs concurrently with telophase, resulting in the formation of two genetically identical daughter cells. The correct order of the stages of mitosis is prophase, metaphase, anaphase, and telophase, reflecting the sequential progression of events during nuclear division.