For those of you unfamiliar with scientific lingo, we’ll begin with the basic definitions of DNA and RNA.
DNA (d eoxyribonucleic acid): DNA is the double-stranded (shaped like a double helix) chemical manual for a living organism. Every organism has DNA, which shows it how to grow, what characteristics to develop, and when to die. DNA is found in every cell of an organism’s body.
DNA controls the phenotype by the synthesis of RNA (ribonucleic acid), which takes place during a process called transcription. RNA then acts to convert the nucleic acid sequence into the amino acid sequence of proteins. A sequence of bases in DNA and RNA may determine the sequence of amino acids for a single protein.
DNA molecules are very long and very thin. One DNA molecule from the chromosome of a mammal is about 1 m long when unraveled. However, it has to fit in a nucleus which is about 5-6 smaller than that. DNA is composed of four different building blocks, the nucleotides. The sequence of nucleotides in the polymers is the storage location of the genetic information carried by the chromosomes. Each nucleotide has three parts.
- a nitrogen base substance called purine
- a sugar called deoxyribose
- a phosphate group
The nitrogenous base determines the identity of the nucleotide, and they are often referred to by their base. (A, C, G, or T) One DNA strand can be up to several million nucleotides in length.
Inside each cell the DNA acts like an instruction manual. It provides all the information it needs to function. The actual work of the translating the information into a medium that can be used by the cell is done by RNA. DNA and RNA have the same ribose group, with one exception: RNA thymine does not occur.
RNA (ribonucleic acid): RNA, unlike DNA, is single-stranded. I t carries single pages of instructions out of the nucleus to places they're needed throughout the cell. It copies ten times faster than DNA, and its performance is error-free. It helps translate the mRNA in the ribosome into amino acids. RNA has three functions:
- It serves as the messenger that tells the ribosome in the cell what protein to make.
- It serves as part of the structure of the ribosome
- It functions to bring amino acids to the ribosome when a specific amino acid is called for.
It is important to know that all organisms that are the same contain the same genetic information. Upon division, each daughter cell obtains an EXACT copy of the DNA of the parent. However, the specific genes that are expressed at specific times may vary between the tissues. These small differences allow for the regulation of development to occur in the organism.
The messenger RNA (mRNA) serves as a medium between DNA and the protein. Parts of the DNA are transcribed into the mRNA.
Ribosomal RNA (or rRNA) composes an essential part of the protein synthesis in the ribosomes. Hundreds of copies of rRNA genes per genome are made.
Transfer RNA (tRNA) carries amino acids to the ribosomes to allow the ribosome to put that amino acid on the protein being synthesized.
DNA and RNA split responsibilities in that the DNA does not always dictate literally the sequence of the protein, but RNA editing can occur.
These processes between DNA and RNA are very intricate. And no wonder. These two tiny substances control the building blocks of life.
By Jessica Maughan