Mitochondrial DNA definition Mitochondrial DNA (mtDNA) refers to the DNA that is located inside the mitochondria, an organelle present in eukaryotic cells. MtDNA is double stranded but, unlike nuclear DNA, is circular, not packaged in chromatin, the translation of its codons into proteins does not follow the rules of the universal genetic code and has […]

Model Organism’s Concept The study of cellular mechanisms, genes, heredity and development of species were only possible due to the use of model organisms. Model organisms are non-human species whose genomes are known and which have genetic mechanisms common to a large group of related organisms. Gregor Mendel was the first to carry out studies using this […]

Molecular Biology is a branch of Biology that studies the cell at a molecular level. It has the main objective of studying the biochemical interactions between the different systems of the cell. It also studies in which way these interactions are regulated, focusing on the relationship between structure and function of genetic material (DNA and […]

Concept of necrosis The term necrosis refers to non-apoptotic, i.e. non-programmed, cell death. Cycle and cell death During its life cycle, cell undergoes several morphologic and structural changes. These changes are known and are characterized and divided into phases: interphase (constituted by G1 phase, S phase and G2 phase) and M phse (constituted by mitosis […]

Northern blot definition Northern blot refers to a technique used in Molecular Biology in which genetic expression is studied through detection of messenger RNA (mRNA) in a sample. This technique makes it possible to determine whether a gene is being transcribed into RNA or not. In addition, it is also possible determine the gene expression […]

Nucleosome definition Nucleosome refers to the fundamental structural unit of chromatin in the eukaryotic cell. It is this protein complex that gives the chromatin the ‘necklace of beads’ aspect. Cell nucleus and chromatine The cell stores all information necessary for its growth, metabolism and division into the nucleus, in the form of DNA. However, if […]

Occluding junction definition Occluding junction refers to the cell junction that seals the space between cells of an epithelium in such a way that it creates a barrier, which prevents the passage of molecules. Cell junctions Tissue cells are in constant communication due to existence of cellular junctions. There are various types of cell junctions […]

Okazaki Fragments definition Okazaki Fragments refers to small single stranded DNA fragments, formed upon DNA replication, more specifically, the back strand.   DNA Replication/Duplication For normal cell growth and division in organisms, an initial step called DNA replication is required. This process is based on semi-conservative copy of DNA in the nucleus of a growing […]

Oocyte I definition Oocyte I designates a female germline diploid cell that forms during the cycle called oogenesis. Mammalian oocytes I enter phase I of meiosis during fetal development. Oocyte I development Oocyte I develops during oogenesis, a cycle through which oogonium develop and produce ovum. This cycle begins in fetal development, where primordial germ […]

Oocyte II definition Oocyte designates a female germline diploid cell that forms during the cycle called oogenesis and derives from oogonium growth. In mammals and most species, oocyte II is a haploid cell derived from the maturation of oocyte I in oogenesis. Oocyte II development At the end of meiosis phase I, in oogenesis, oocyte […]