In molecular biology

Molecular biology

Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

 and genetics

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

, a blot is a method of transferring protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 or RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

, onto a carrier (for example, a nitrocellulose

Nitrocellulose

Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...

 PVDF or nylon

Nylon

Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...

 membrane). In many instances, this is done after a gel electrophoresis

Gel electrophoresis

Gel electrophoresis is a method used in clinical chemistry to separate proteins by charge and or size and in biochemistry and molecular biology to separate a mixed population of DNA and RNA fragments by length, to estimate the size of DNA and RNA fragments or to separate proteins by charge...

, transferring the molecules from the gel

Gel

A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...

 onto the blotting membrane, and other times adding the samples directly onto the membrane. After the blotting, the transferred proteins, DNA or RNA are then visualized by one or more different methods:

• colorant staining (for example, silver staining of proteins)
• autoradiographic visualization of radioactive labelled molecules (performed before the blot)
• specific labelling of some proteins or nucleic acid
  Nucleic acid
  Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...
  
  s. It is done with antibodies
  Antibody
  An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
  
   or hybridization probe
  Hybridization probe
  In molecular biology, a hybridization probe is a fragment of DNA or RNA of variable length , which is used in DNA or RNA samples to detect the presence of nucleotide sequences that are complementary to the sequence in the probe...
  
  s that bind only to some molecules of the blot and have an enzyme
  Enzyme
  Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
  
   joined to them. After proper washing, this enzymatic activity (and so, the molecules we search in the blot) is visualized by incubation with proper reactive, rendering either a colored deposit on the blot or a chemiluminiscent reaction which is registered by photographic film
  Film
  A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
  
  .

Common blot methods are :

• Southern blot
  Southern blot
  A Southern blot is a method routinely used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. The method is named...
  
   for DNA
  DNA
  Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
  
  
• Southwestern blot
  Southwestern blot
  Southwestern blotting, based along the lines of Southern blotting and first described by B. Bowen and colleagues in 1980, is a lab technique which involves identifying and characterizing DNA-binding proteins by their ability to bind to specific oligonucleotide probes...
  
   for Protein-DNA
• Northern blot
  Northern blot
  The northern blot is a technique used in molecular biology research to study gene expression by detection of RNA in a sample. With northern blotting it is possible to observe cellular control over structure and function by determining the particular gene expression levels during differentiation,...
  
   for RNA
  RNA
  Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
  
  
• Reverse Northern blot
  Reverse Northern blot
  The reverse northern blot is a variant of a northern blot in which the nucleic acid immobilized on a membrane is a collection of isolated DNA fragments rather than RNA, and the probe is RNA extracted from a tissue and radioactively labelled....
  
   for RNA
  RNA
  Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
  
  
• Western blot
  Western blot
  The western blot is a widely used analytical technique used to detect specific proteins in the given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide...
  
   for protein
  Protein
  Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
  
  s
• Far-Western blot for Protein-Protein
• Eastern blotting
  Eastern blotting
  Eastern blotting is a biochemical technique used to analyze protein post translational modifications such as lipids and glycoconjugates. It is most often used to detect carbohydrate epitopes. Thus, Eastern blotting can be considered an extension of the biochemical technique of Western blotting...
  
   for posttranslational modification
  Posttranslational modification
  Posttranslational modification is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins....
  
  
• Far-Eastern blot
  Far-Eastern blot
  Far-Eastern blotting is a technique developed in 1994 by Taki and colleagues at the Tokyo Medical and Dental University, Japan for the analysis of lipids separated by high-performance thin layer chromatography...
  
   for Lipids, Drugs
  DRUGS
  Destroy Rebuild Until God Shows are an American post-hardcore band formed in 2010. They released their debut self-titled album on February 22, 2011.- Formation :...
  
   and Hormones
• Dot blot
  Dot blot
  right|thumb|350px|Schematic of the use of two [[Allele specific oligonucleotide|ASO]] probes on duplicate Dot-blot filters.A Dot blot is a technique in molecular biology used to detect biomolecules. It represents a simplification of the northern blot, Southern blot, or western blot methods...
  
  
• Slot blot