• Zoology

    EAR ANATOMY

    The ear is the organ found in animals which are designed to perceive sounds. Most animals have some sort of ear to perceive sounds, which are actually high-frequency vibrations caused by the movement of objects in the environment. The human ear picks up and interprets high-frequency vibrations of air, while the sound-sensing organs of aquatic animals are designed to pick up high-frequency vibrations in water. Most vertebrates have two ears: one on either side of the head. In some animals, including most mammals, the ear is also used for balance. In humans, the inner ear contains parts called the semicircular canals, where otoliths – tiny stone-like structures – shift in…

  • Biochemistry,  Cell biology

    CELL MEMBRANE

    The cell membrane, also known as the plasma membrane, is a double layer of lipids and proteins that surrounds a cell and separates the cytoplasm (the contents of the cell) from its surrounding environment. It is selectively permeable, which means that it only lets certain molecules enter and exit. It can also control the amount of some substances that go into or out of the cell. All cells have a cell membrane.  Function of the Cell Membrane The cell membrane gives the cell its structure and regulates the materials that enter and leave the cell. Like a drawbridge intended to protect a castle and keep out enemies, the cell membrane only…

  • Biochemistry,  Cell biology,  Genetics

    RNA

    Structurally speaking, ribonucleic acid (RNA), is quite similar to DNA. However, whereas DNA molecules are typically long and double-stranded, RNA molecules are much shorter and are typically single-stranded. RNA molecules perform a variety of roles in the cell but are mainly involved in the process of protein synthesis (translation) and its regulation. RNA Structure RNA is typically single-stranded and is made of ribonucleotides that are linked by phosphodiester bonds. A ribonucleotide in the RNA chain contains ribose (the pentose sugar), one of the four nitrogenous bases (A, U, G, and C), and a phosphate group. The subtle structural difference between the sugars gives DNA added stability, making DNA more suitable for storage of genetic information,…

  • Genetics

    MUTATION

    At the simplest level, a mutation is a change or transformation. In biology, mutations refer to changes in chromosomes and genes, which typically manifest physically. The effect of a mutation can depend on the region in which the sequence of genetic material has been changed. The simplest and the most harmless are substitutions of a single base pair with another, with no effect on the protein sequence. At the other end are insertion or deletion mutations that lead to non-functional gene products. Mutations can also occur on a large scale, with long stretches of DNA (or RNA when it is the genetic material) being inverted, inserted, duplicated, deleted, transposed or translocated. The…

  • Biochemistry,  Cell biology,  Genetics

    DNA REPLICATION

    DNA duplicates itself with complete fidelity for passing on genetic information to the next generation of cells. Replication may thus be defined as a mechanism for transmission of genetic information generation after generation. DNA Replication is Semi-Conservative DNA replication of one helix of DNA results in two identical helices. If the original DNA helix is called the “parental” DNA, the two resulting helices can be called “daughter” helices. Each of these two daughter helices is a nearly exact copy of the parental helix (it is not 100% the same due to mutations). DNA creates “daughters” by using the parental strands of DNA as a template or guide. Each newly synthesized…

  • Biology,  Genetics

    Johann Gregor Mendel (1822-1884) Father of Genetics

    Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits. He recognized the mathematical patterns of inheritance from one generation to the next. Mendel’s Laws of Heredity are usually stated as: 1) The Law of Segregation: Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele…

  • Genetics

    GENETIC CODE

    Early studies on the nature of the genetic code showed that the DNA base sequence corresponds to the amino acid sequence of the polypeptide specified by the gene. That is, the nucleotide and amino acid sequences are colinear. It also became evident that many mutations are the result of changes of single amino acids in a polypeptide chain. However, the exact nature of the code was still unclear. Establishment of the Genetic Code Since only 20 amino acids normally are present in proteins, there must be at least 20 different code words in a linear, single strand of DNA. The code must be contained in some sequence of the four…

  • Biochemistry

    RIBOSOMES

    While examining the animal and plant cell through a microscope, you might have seen numerous organelles that work together to complete the cell activities. One of the essential cell organelles are ribosomes, which are in charge of protein synthesis. The ribosome is a complex made of protein and RNA and which adds up to numerous million Daltons in size and assumes an important part in the course of decoding the genetic message reserved in the genome into protein. The essential chemical step of protein synthesis is peptidyl transfer, that the developing or nascent peptide is moved from one tRNA molecule to the amino acid together with another tRNA. Amino acids…

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