Nucleic Acids:

Living organisms are complex systems. Hundreds of thousands of proteins exist inside each one of us to help carry out our daily functions (see our Fats and Proteins module for more information). These proteins are produced locally, assembled piece-by-piece to exact specifications. An enormous amount of information is required to manage this complex system correctly. This information, detailing the specific structure of the proteins inside of our bodies, is stored in a set of molecules called nucleic acids.

The nucleic acids are very large molecules that have two main parts. The backbone of a nucleic acid is made of alternating sugar and phosphate molecules bonded together in a long chain, represented below:

sugar	phosphate	sugar	phosphate	...

Each of the sugar groups in the backbone is attached (via the bond shown in red) to a third type of molecule called a nucleotide base:

nucleotide base		nucleotide base
|		|
sugar	phosphate	sugar	phosphate	...

Though only four different nucleotide bases can occur in a nucleic acid, each nucleic acid contains millions of bases bonded to it. The order in which these nucleotide bases appear in the nucleic acid is the coding for the information carried in the molecule. In other words, the nucleotide bases serve as a sort of genetic alphabet on which the structure of each protein in our bodies is encoded.

Proteins

Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by a gene and encoded in the genetic code. Although this genetic code specifies 20 "standard" amino acids plus selenocysteine and - in certain archaea - pyrrolysine, the residues in a protein are sometimes chemically altered in post-translational modification. This can happen either before the protein is used in the cell, or as part of control mechanisms. Proteins can also work together to achieve a particular function, and they often associate to form stable complexes..


Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in every process within cells. Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. Proteins are also necessary in animals' diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism..

DNA-RNA-Protein

DNA carries the genetic information of a cell and consists of thousands of genes. Each gene serves as a recipe on how to build a protein molecule. Proteins perform important tasks for the cell functions or serve as building blocks. The flow of information from the genes determines the protein composition and thereby the functions of the cell.

The DNA is situated in the nucleus, organized into chromosomes. Every cell must contain the genetic information and the DNA is therefore duplicated before a cell divides (replication). When proteins are needed, the corresponding genes are transcribed into RNA (transcription). The RNA is first processed so that non-coding parts are removed (processing) and is then transported out of the nucleus (transport). Outside the nucleus, the proteins are built based upon the code in the RNA (translation.

DNA:

The genetic material of organisms is made up of nucleic acids. There are two types of nucleic acids namely Deoxyribonucleic Acid ( DNA) and Ribonucleic Acid (RNA). In most organisms DNA forms the genetic material, while some viruses contain only RNA, which forms the sole genetic material. DNA is a macromolecule and it has a high molecular weight.

Genes are made up of DNA and they are located on the chromosome. Genes are always present on the chromosome at specific sites. DNA is the genetic material of the cell. It carries information in a coded form from cell to cell and from parents to offspring. The combination of a nitrogenous base and a pentose sugar forms what is called a nucleoside.

The addition of phosphate groups to the nucleoside gives rise to nucleotide. DNA is a long linear polymer of nucleotides. DNA is responsible for expression of genetic characters. The genetic information flows from DNA to RNA and from RNA to protein. The concepts constitute the central dogma of molecular biology. The information contained in DNA and in RNA is based on 4 nucleotides. These four nucleotides carry the genetic code which is read in groups of three nucleotides.


Protein synthesis occurs in three different steps. The process by which an enzyme system converts the genetic information of a segment of DNA or template DNA into an RNA strand with a base sequence complementary to one of the DNA strands is called Transcription

STEM CELLS AND IT TYPES.

STEM CELLS :

A special type of "source" or "starter" cell that has the ability to grow into adult tissue. Stem cells are the foundation for every organ, tissue and cell in the human body. Stem cells may be able to repair or replace damaged tissue, thereby reversing diseases and injuries such as cancer, diabetes, cardiovascular disease and blood diseases, to name a few.

TYPES OF STEM CELLS:

There are two types of stem cells — unlimited stem cells (also known as embryonic stem cells) and limited stem cells (also known as adult stem cells).

Unlimited stem cells are currently obtained with patients' permission from leftover three-day old embryos that would otherwise be discarded from fertility clinics. These embryos are created and exist entirely outside the body. Unlimited stem cells can develop into any kind of cell type or tissue in the body.

Limited stem cells are rare cells that can be found in only some developed organs or tissues. Limited stem cells have been successfully used for some time now in bone marrow transplants (either with bone marrow stem cells or umbilical cord blood stem cells) and skin and hair transplants. There is also another potential way to get embryonic stem cells using an unfertilized egg and an adult cell from the patient. However, this is still being studied

RNA

Ribonucleic acid (RNA) is a nucleic acid that consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details: in the cell, RNA is usually single-stranded, while DNA is usually double-stranded; RNA nucleotides contain ribose while DNA contains deoxyribose (a type of ribose that lacks one oxygen atom); and RNA has the base uracil rather than thymine that is present in DNA.RNA is transcribed from DNA by enzymes called RNA polymerases and is generally further processed by other enzymes. RNA is central to the synthesis of proteins. Here, a type of RNA called messenger RNA carries information from DNA to structures called ribosomes. These ribosomes are made from proteins and ribosomal RNAs, which come together to form a molecular machine that can read messenger RNAs and translate the information they carry into proteins. There are RNAs with other roles – in particular regulating which genes are expressed, but also as the genome of most viruses

Introduction to DNA

Deoxyribonucleic acid(DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, or a code, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.

Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.

Within cells, DNA is organized into structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, fungi, and protists) store their DNA inside the cell nucleus, while in prokaryotes (bacteria and archae) it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.