Meiosis, DNA Replication, Transcription, and Translation
Meiosis: Maintaining Chromosome Number
This division is necessary for the formation of gametes during sexual reproduction in order to keep the number of chromosomes of each species, generation after generation. Meiosis gives rise to 4 daughter cells, each with half the chromosomes as the parent cell.
Haploid and Diploid Cells
Haploid cells have half the number of chromosomes and contain one copy of genetic information. Diploid cells have the full number of chromosomes (n) and contain two complete copies
Read MoreViruses and the Immune System: Defense Mechanisms
Viruses: Structure and Cycles
Viruses are supramolecular complexes composed of proteins, nucleic acids, and, in some cases, lipids. They are considered genetic factors in transit. When a virus is outside the cell, it is called a virion. Viruses are intracellular parasites, not cells. They can be classified by the type of nucleic acid (RNA in retroviruses, DNA in adenoviruses), by the presence or absence of an envelope, and by the type of host they infect (bacteria in bacteriophages, other cells in
Read MoreHuman Anatomy: Cerebellum, Liver, Medulla, Spinal Cord, and Heart
Cerebellum
The cerebellum is a region of the brain whose main function is to integrate sensory and motor pathways. There are a lot of nerves that connect the cerebellum to other brain structures and the spinal cord. The cerebellum integrates all information received to refine and control commands sent to the cerebral cortex’s locomotor pathways. The cerebellum is an unpaired organ, located in the posterior cranial fossa, dorsal to the brainstem, and below the occipital lobe. It has a central portion,
Read MoreDilute and Concentrated Urine Formation: Renal Mechanisms
Mechanisms of Formation of Dilute Urine
In extreme situations of hydration (overload):
- Proximal tubule: Resorption is equivalent to water reabsorption. The osmolarity is constant.
- Descending loop of Henle: The renal medulla is the only part of the body that is hyperosmolar, and it becomes more hyperosmolar the deeper we go towards the calyces. Water moves into the interstitium, and there is no solute reabsorption (increasing intratubular osmolarity).
- Ascending loop of Henle: The osmolarity decreases
Cell Cycle Phases: Mitosis and Meiosis Explained
Cell Cycle
The cell cycle is a series of changes undergone by the cell from which it is formed until it divides.
Interphase
Interphase is a period that elapses between two successive mitoses (cell divisions). It occupies most of the cell cycle, and cell metabolic activity increases in size.
There are three periods:
- Phase G1: Covers the period between division and DNA synthesis. Mainly, proteins are synthesized, and the cell enlarges. In cells that do not divide, this phase is ongoing and is called G0.
Human Coordination Systems: Nervous and Endocrine
Coordination Systems
People perform different functions: we move, breathe, digest food, excrete waste substances, and so on. To perform all these functions, we need to interact with the environment, both externally and internally. Using the function of relationship, people, like all other living things, receive information and prepare responses.
To perform the function of relationship, people need to have a coordination system that allows us to detect changes that occur in the environment, analyze
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