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  Gene Silencing : A brief review  Controlling the expression of genes is a phenomenon known as gene silencing. There are two ways to regulate gene expression: translation and transcription. Gene silencing and gene knockdown, in which gene expression is decreased, are quite similar. It must be distinguished from gene knockout, which is the total removal of a gene from the genome. Silencing of Transcriptional Genes Transcriptional gene silencing is the term used to describe the silencing of genes at the transcriptional level. It is a process of alteration in which the machinery of transcription is disabled. The techniques for transcriptional gene silencing are as follows: Mendelian inheritance is the basis for the epigenetic approach known as genomic imprinting. The genes that children acquire from their parents determine how those genes are expressed in them. Histone modification or DNA methylation silences the gene, which is passed down unchanged to the progeny. Paramutatio...

Progymnosperms : a brief illustration  What Progymnosperms Mean: It is currently believed that some fossils from the Devonian and Carboniferous eras of the Paleozoic era, which were formerly believed to belong to pteridophytes (Primofilices), are more closely related to gymnosperms even though they are not fully gymnospermous. Following the discovery of similarities between the fern-like fronds of Archaeopteris and the gymnosperm-like trunks of Callixylon, these fossils were categorized by Beck (1960) as belonging to the Progymnospermopsida class of gymnosperms. Progymnosperms are defined as "plants exhibiting the features of gymnospermic anatomy and ptendophytic reproduction," according to Bonamo (1975).  From the Middle Devonian through the Lower Mississippian, prosims were an essential part of the vegetation. They were somewhat similar to gymnosperms, as their name suggests. Similar to true gymnosperms, progymnosperms also frequently developed wood by secondary growth of t...

 Use of  apomixis in Plant Breeding  The Greek terms "APO" (away from) and "mixed" (the process of mixing or mingling) are the roots of the word "apomixis." It describes how a plant grows from a seed without the need for fertilization or typical sexual reproduction. The easiest way to define apomixis is as a reference to the asexual process. The resultant plant is a female parent plant clone. The female gametophyte, or embryo sac, is created during sexual reproduction by developmental processes that take place inside the ovule. After double fertilization, the resultant components are the embryo and endosperm. In higher plants, apomixis is a common occurrence. More than 35 groups of plants, including the Gramineae, Rosaceae, Compositae, and Rutaceae, are known to be apomictic. Apomixis is seen in major grains like wheat and maize. Apomixis Types There are three commonly known kinds of apomixis: adventitious embryony, apospory, and diplospory. Diplospory T...

Reverse Transcription Basics The process of creating DNA from an RNA template is known as reverse transcription. Reverse transcriptases, or RNA-dependent DNA polymerases, are the enzymes that propel this process.  Reverse transcriptases are found in retroviruses and prokaryotic and eukaryotic organisms in their natural states. When a viral particle enters a target cell's cytoplasm, reverse transcription starts. As a component of an as-yet-uncharacterized nucleoprotein complex, the viral RNA genome penetrates the cytoplasm. Through a complex set of steps, reverse transcription creates a linear DNA duplex in the cytoplasm. Although the DNA and its RNA template are colinear, the DNA has terminal duplications called long terminal repeats (LTRs) that are absent from viral RNA.  Current reverse transcription models suggest that in order to produce the LTRs, two specific template switches called "jumps" or strand-transfer reactions are needed. The two unique enzymatic activities...

Evolution of sex in algae : An overview  In plants, asexual and sexual reproduction are the two main modes of reproduction. Asexual reproduction does not entail sex and does not involve the fusing of any kind of cell or gamete. Spores are a unique form of cell that reproduces in this manner. Every one of these spores has the ability to grow into a new plant. In contrast, when two cells, or gametes, combine during sexual reproduction, a zygote is created that eventually grows into a new plant. Without fusing, individual gametes are normally unable to create new plants. Origin of sex:  The most primitive algae, such as those belonging to the Cyanophyceae (Myxophyceae) family, such as Gloeocapsa and Chroococcus, reproduce by fusion, whereas Oscillatoria, Nostoc, and Anabaena, among others, reproduce vegetatively through the division of a small group of cells known as hormogonia, which subsequently gives rise to new plants through additional division. Certain Cyanophyceae members ...

  Importance of cell wall in prokaryotic cell wall: A cell wall is defined as the non-living component, covering the outmost layer of a cell. Its composition varies according to the organism and is permeable in nature.   All prokaryotic cells have a stiff cell wall, located underneath the capsule (if there is one). This structure maintains the cell shape, protects the cell interior and prevents the cell from bursting when takes up the water.  The main function of the cell wall is to provide structural strength and support, and also provide a semi-permeable surface for molecules to pass in and out of the cell. The cell wall in bacteria is essential for survival as it helps to keep the contents of the cell intact. Antibiotics usually work on this principle by targeting the bacterial cell wall and causing lysis. This leads to the expulsion of cellular contents and the eventual death of the cell. Importance of cell wall in Eukaryotic cell wall:      A typi...

Retrovirus  - an overview Retroviruses are viruses whose genetic material is RNA. They are retroviruses that are members of the Retroviridae family. After infecting a cell, it uses reverse transcription to change the RNA therein into DNA. After that, the host cell's DNA is exposed to this viral DNA, and it begins to replicate there. The Human Immunodeficiency Virus (HIV), for instance. Structure of Retroviruses Meaning of a retrovirus: A class of RNA viruses that replicate by introducing a DNA copy of their genome into their host cell. The envelope protein complex is embedded in the lipid bilayer, which is composed of two concentric outer circles. Hexagonal proteins make up capsids. The RNA genome is replicated in a loop that is held together by nucleoproteins.   The principal parts of a virion are: Wallet Env genes encode glycoproteins and lipids that make up the retroviral envelope. It fulfills three crucial purposes: Envelope  Env genes encode glycoproteins and lipids ...