A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion.

In quantum physics, organic chemistry, and biochemistry, the distinction from ions is dropped and molecule is often used when referring to polyatomic ions.

In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. This relaxes the requirement that a molecule contains two or more atoms, since the noble gases are individual atoms.

A molecule may be homonuclear, that is, it consists of atoms of one chemical element, e.g. two atoms in the oxygen molecule (O2); or it may be heteronuclear, a chemical compound composed of more than one element, e.g. water (two hydrogen atoms and one oxygen atom; H2O).

Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not considered single molecules.

Molecular technology is a broad term that involves different laboratory techniques to study or modify DNA, RNA, or proteins. There are different types of molecular technologies available to help us advance medicine, agriculture, forensics, and many other fields. For example, you may recall that recombinant DNA involves combining two sources of DNA to create new genetic information. This is a type of molecular technology that can be used to manufacture insulin to treat diabetes when we place the gene for insulin into bacteria.

Molecular technology uses different lab techniques to study and modify DNA, RNA, or proteins for different applications (for example, medicine, agriculture, or forensics).

Molecular Biology Techniques DNA cloning, cut and paste DNA, bacterial transformation , transfection, chromosome integration, cellular screening, cellular culture, extraction of DNA, DNA polymerase DNA dependent, reading and writing DNA, DNA sequencing, DNA synthesis, molecular hybridization , rewriting DNA : mutations, random mutagenesis, point mutation, chromosome mutation. Most important techniques are Polymerase chain reaction (PCR), Expression cloning, Gel electrophoresis, Macromolecule blotting and probing, Arrays (DNA array and protein array).

Humans share 99% of their DNA with chimpanzees. One way to see if two organisms are evolutionarily related is to study their morphology, or physical characteristics, and look for similarities. The bone structure of our hand is more similar to that of a chimpanzee and less similar to that of a frog. So, on this basis, we can say that we are more closely related to chimpanzees than to frogs. Beside morphology, another way to examine evolutionary relationships between organisms is to study their molecular similarities, which can be done by comparing DNA or protein sequences.

Bioinformatics is a field of study that combines biology and computer science, making it possible to analyze huge amounts of biological data. The genome of humans and that of chimpanzees are extremely massive, and comparing them manually would be nearly impossible! Using computers, we can line up these two sequences and see what is similar and what is different.

In the case of humans and chimpanzees, there is only about a 1% difference in DNA sequences. This shows a strong evolutionary relationship between us and chimpanzees.