“Molecular genetics” sounds as though it should refer to the genetics of molecules, but this doesn’t make much sense. It actually refers to the physical and chemical properties of genes. These genes are units of heredity that are stored inside cells, and passed down through generations.
The Chemical Structure of DNA
DNA is a long molecule with a double helix structure, which is sometimes compared to a “spiral staircase”. On each strand there are structural units called nucleotides, which include chemicals called bases. These bases are paired along the double helix to form the “stairs” (see image 1). They are:
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
The bases of one strand pair up with the bases on the other strand, and are held by a hydrogen bond. This pairing is not random. Adenine always pairs with thymine and cytosine always pairs with guanine. This means that from only one strand of DNA, it is possible to work out the chemicals on the missing strand.
The Chemical Structure of RNA, and Gene Expression
Ribonucleic acid (RNA) is similar to DNA. RNA is a one-stranded molecule, and is made of different sugars. It also has the chemical base uracil in place of thymine. On paper, a DNA strand can be coded from RNA simply by keeping this difference in chemical bases in mind. For example, the RNA sequence AUUGGC corresponds to the DNA sequence TAACCG.
Inside the cell’s nucleus, messenger RNA (mRNA) takes a copy of DNA. It then leaves the nucleus, where organelles called ribosomes read this information to make proteins. The term “gene expression” is used to describe this process of transcription and translation that leads to the production of a protein.
Molecular Genetics and Gene Mutations
Another area of interest to molecular geneticists is how genes mutate. Gene mutations are changes in an organism’s DNA. In humans, such changes can happen before or after fertilization, including when a person is fully grown. Although most mutations aren’t harmful, there are some that have implications for health and development.
Molecular Genetics and Gene Therapy
Gene therapy also comes under the umbrella of molecular genetics, and is concerned with inserting new genes into organisms. Gene therapy techniques vary, but generally the idea is to fix faulty genes that cause disease. The new genes are in inserted into the organism’s cells using a carrier molecule, such as a virus.
For more information, read the Molecules of Genetics section on the DNA From the Beginning website.
Sources
The cells, tissue and organisations of the body, Anatomy and Physiology (9th edition),published by Ross and Wilson in 2001, authors Anne Waugh and Alison Grant.
"How do genes direct the production of proteins?", Genetics Home Reference website, published: May 29th 2009, accessed: 7th June 2009, no author specified.
"Mutations and Health", Genetics Home Reference, published: May 29th 2009, accessed: 7th June 2009, no author specified.
"Gene Therapy", Human Genome Project Information website, last modified: 9th February 2009, accessed: 7th June 2009.
 |
 |
