What is DNA?
DNA stands for deoxyribonucleic acid. Its structure helps determine what we look like and how we function at our core level. We have genes that give us the traits that make us who we are. In simple terms, DNA determines what we look like, while RNA makes proteins that carry out the instructions that control the growth and function of cells.
In humans, DNA contains approximately 6 billion base pairs, while proteins require 20,000–30,000 base pairs to code for the thousands of different kinds of protein. However, this does not mean that everything about human genetics is encoded in DNA.
The vast majority of our genetic information is stored in non-coding regions of DNA; meaning, that they do not encode for genes (protein coding) themselves. Instead, these parts of DNA act as a kind of framework or scaffolding on which genes are put together. Thus, DNA is responsible for directing the synthesis of both genes and proteins.
There are two types of DNA molecules:
- single-stranded DNA or ssDNA;
- double-stranded DNA or dsDNA.
Each type of molecule serves a specific role in gene expression.
The double helix structure is similar to the way humans make use of two interlocking pieces of paper that are folded over each other.
By doing this they create a strong and sturdy file folder. The base pairs that are held together in a double helix formation are adenine (A), cytosine (C) guanine (G) and thymine (T).
These bases are arranged in a particular pattern according to their chemical composition. In this illustration we have shown them in order from left to right; A, T, G, C. When these four nucleotides bond together, the result is called deoxyribonucleic acid (DNA).
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What is RNA?
RNA stands for Ribonucleic Acid. This molecule is an intermediary structural molecule between DNA (deoxyribonucleic acid) and protein. More specifically, RNA is a single-stranded nucleic acid that consists of nucleotides composed of four different bases (A, G, C and U).
In addition, there are two forms of RNA called ribosomal RNA (rRNA) and transfer RNA (tRNA), which make up the basic building blocks of a ribosome. A ribosome is a molecular machine responsible for translating mRNA into polypeptide chains, which ultimately serve as the raw material of proteins.
Structure of RNA
The typical shape of RNA contains three parts: the backbone, the phosphate groups and the sugar moieties. There are many variations in the shapes of RNA molecules, but they generally have the following characteristics:
Most RNA molecules consist of a long chain of nucleotides linked together via phosphodiester bonds. However, some RNAs are not constructed of a continuous string of nucleotides, but rather have a helical shape where the individual nucleotides are connected at regular intervals along the length of the strand.
b.) Phosphate Groups
RNAs tend to have negatively charged phosphate groups attached to them. These negatively charged phosphate groups help stabilize the RNA nucleotide chains.
c.) Sugar Moieties
Sugars are often found at specific locations along the backbones of RNA strands. Sugars may be present at the 5′ end of the RNA strand or sometimes near the 3′ end of the strand. When present at the 5′ ends, these sugars act as “cap structures,” protecting the RNA’s coding sequences from being degraded by cellular enzymes.
Functions of RNA
RNA performs several functions, including the following:
- Translation involves the transfer of genetic information from RNA (messenger RNA) to proteins. RNA polymerase II transcribes messenger RNAs from DNA by RNA polymerase.
- Transcription begins at the start site, which is often located either upstream from or within genes.
- After transcription, messenger RNA undergoes processing steps, including capping, splicing, and cleavage. Then translation takes place.