When cells make enzymes, especially proteases, they often make them as zymogen, an inactive form of the enzyme. ... For example: PROthrombin is the zymogen form of thrombin, an enzyme involved in blood clotting. PepsinoGEN is the zymogen form of pepsin, the enzyme found in your stomach that helps digest food. An example of zymogen is pepsinogen. Pepsinogen is the precursor of pepsin. Pepsinogen is inactive until it is released by chief cells into HCl.

Gene expression in eukaryotic cells is regulated by repressors as well as by transcriptional activators. Like their prokaryotic counterparts, eukaryotic repressors bind to specific DNA sequences and inhibit transcription. ... Other repressors compete with activators for binding to specific regulatory sequences. Eukaryotic cells have a true nucleus, which means the cell's DNA is surrounded by a membrane. Therefore, the nucleus houses the cell's DNA and directs the synthesis of proteins and ribosomes, the cellular organelles responsible for protein synthesis.

Data retrieval means obtaining data from a database management system such as ODBMS. ... Then the Database Management System (DBMS), software for managing databases, selects the demanded data from the database. The retrieved data may be stored in a file, printed, or viewed on the screen. SRS (Sequence Retrieval System) is an information indexing and retrieval system designed for libraries with a flat file format such as the EMBL nucleotide sequence databank, the SwissProt protein sequence databank or the Prosite library of protein subsequence consensus patterns.

DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. Replication is an essential process because, whenever a cell divides, the two new daughter cells must contain the same genetic information, or DNA, as the parent cell. 

• Step 1: Replication Fork Formation. Before DNA can be replicated, the double stranded molecule must be “unzipped” into two single strands. ...
• Step 2: Primer Binding. The leading strand is the simplest to replicate. ...

• Step 3: Elongation - Enzymes known as DNA polymerases are responsible creating the new strand by a process called elongation. There are five different known types of DNA polymerases in bacteria and human cells. In bacteria such as E. coli, polymerase III is the main replication enzyme, while polymerase I, II, IV and V are responsible for error checking and repair. DNA polymerase III binds to the strand at the site of the primer and begins adding new base pairs complementary to the strand during replication. In eukaryotic cells, polymerases alpha, delta, and epsilon are the primary polymerases involved in DNA replication. Because replication proceeds in the 5' to 3' direction on the leading strand, the newly formed strand is continuous.

  The lagging strand begins replication by binding with multiple primers. Each primer is only several bases apart. DNA polymerase then adds pieces of DNA, called Okazaki fragments, to the strand between primers. This process of replication is discontinuous as the newly created fragments are disjointed.

  Step 4: Termination
  Once both the continuous and discontinuous strands are formed, an enzyme called exonuclease removes all RNA primers from the original strands. These primers are then replaced with appropriate bases. Another exonuclease “proofreads” the newly formed DNA to check, remove and replace any errors. Another enzyme called DNA ligase joins Okazaki fragments together forming a single unified strand. The ends of the linear DNA present a problem as DNA polymerase can only add nucleotides in the 5′ to 3′ direction. The ends of the parent strands consist of repeated DNA sequences called telomeres. Telomeres act as protective caps at the end of chromosomes to prevent nearby chromosomes from fusing. A special type of DNA polymerase enzyme called telomerase catalyzes the synthesis of telomere sequences at the ends of the DNA. Once completed, the parent strand and its complementary DNA strand coils into the familiar double helix shape. In the end, replication produces two DNA molecules, each with one strand from the parent molecule and one new strand.

A primer is a short, single-stranded DNA sequence used in the polymerase chain reaction (PCR) technique. In the PCR method, a pair of primers is used to hybridize with the sample DNA and define the region of the DNA that will be amplified. Primers are also referred to as oligonucleotides. Primers are short sequences of complementary DNA which bind to certain nucleotide sequences along the DNA strand. ... These enzymes start off by binding to the primers and then extend the primers by adding new nucleotides to the 3' end, using the single stranded DNA as a template.

Vegetative propagation is an asexual method of plant reproduction that occurs in its leaves, roots and stem. This can occur through fragmentation and regeneration of specific vegetative parts of plants.

The vegetative plant structures arising from the stem are known as rhizomes, bulbs, runners, tubers, etc. The plants propagated vegetatively are given below:

Stem

Runners grow horizontally above the ground. The buds are formed at the nodes of the runners.

Roots

New plants emerge out of swollen, modified roots known as tubers. Buds are formed at the base of the stem.

Leaves

Leaves of a few plants get detached from the parent plant and develop into a new plant.

Bulbs

Bulbs have an underground stem to which the leaves are attached. These leaves are capable of storing food. The centre of the bulb contains an apical bud that produces leaves and flowers. Shoots are developed from the lateral buds.

Therapeutic proteins as drug substance may be provided in individual containers prior to the formulation/filling process. To ensure homogeneity, the therapeutic protein may need to be gently mixed in a vessel prior to filling. In this case, mixing may be necessary. Different types of methods utilized for mixing the material may be employed. Examples of mixing techniques include impellers on a shaft with open processing, suspended impellers, or magnetic stir bars at the bottom of the mixing vessel. It is likely that the mixing process will need to be scaled down for testing in the laboratory. Impeller mixing as well as mixing with magnetic stir bars may be simulated at a small scale. The investigator should determine the appropriate mixing speeds that will be utilized in manufacturing and determine if these processes adversely affect the protein. Studies have been reported for therapeutic proteins that have been mixed using magnetic stir bars, and it was demonstrated that this type of mixing may induce aggregates.

Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in protein synthesis in the cells of the organism. Proteins are the major source of nitrogen in food.

Growth of vertebrate cells in culture requires rich media containing essential amino acids, vitamins, and peptide or protein growth factors, frequently provided by serum. ... Primary cells, which are derived directly from animal tissue, have limited growth potential in culture and may give rise to a cell strain. Cell culture media generally comprise an appropriate source of energy and compounds which regulate the cell cycle. A typical culture medium is composed of a complement of amino acids, vitamins, inorganic salts, glucose, and serum as a source of growth factors, hormones, and attachment factors.

Gene expression in eukaryotic cells is regulated by repressors as well as by transcriptional activators. Like their prokaryotic counterparts, eukaryotic repressors bind to specific DNA sequences and inhibit transcription. ... Other repressors compete with activators for binding to specific regulatory sequences. Because host chromosomal genes are not synthesized at this point, these products are the only proteins synthesized. ... The T7 RNA polymerase then transcribes this gene at high levels, resulting in high production of the factor VIII protein in the bacteria.

Bioinformatics has become an important part of many areas of biology. ... It plays a role in the text mining of biological literature and the development of biological and gene ontologies to organize and query biological data. It also plays a role in the analysis of gene and protein expression and regulation. Biological databases play a central role in bioinformatics. They offer scientists the opportunity to access a wide variety of biologically relevant data, including the ge- nomic sequences of an increasingly broad range of organisms.

mRNA is synthesized in the nucleus using the nucleotide sequence of DNA as a template. ... The process of making mRNA from DNA is called transcription, and it occurs in the nucleus. The mRNA directs the synthesis of proteins, which occurs in the cytoplasm. During translation, an mRNA sequence is read using the genetic code, which is a set of rules that defines how an mRNA sequence is to be translated into the 20-letter code of amino acids, which are the building blocks of proteins.

Many proteins have a quaternary structure, which consists of several polypeptide chains that associate into an oligomeric molecule. Each polypeptide chain in such a protein is called a subunit. ... In domain swapping, a secondary or tertiary element of a monomeric protein is replaced by the same element of another protein. Many protein molecules are composed of more than one subunit, where each subunit is a separate polypeptide chain and can form a stable folded structure by itself. In structural biology, a protein subunit is a single protein molecule that assembles (or "coassembles") with other protein molecules to form a protein complex. Some naturally occurring proteins have a relatively small number of subunits and therefore described as oligomeric, for example hemoglobin or DNA polymerase.