DNA and RNA Structure/Function

Introduction: DNA (deoxyribonucleic acid) is the genetic material and is largely found in the chromosomes. RNA (ribonucleic acid) is made up of nucleotides containing sugar ribose. When these two work together, they build the amino acid sequence in a protein. This section is going to look at them individually.

DNA

Here is the structure of a DNA. As many have heard, or possibly made models of, the DNA is a double helix. This simply means it has two strands that spiral around each other. In the middle of these strands are nucleotides that are bonded by hydrogen bonding. The bonds created are: A with T, and G with C. These are called complimentary paired bases.

This colorful DNA structure image was found at www.biologycorner.com.

The function of DNA is to replicate. Its job is to make an exact replica of itself. The fancy scientific term for this process is called: DNA replication. Here is a brief explanation of how DNA replicates. This is pulled straight from our text book, but I found it to be the simplest and most clear.

1. Before replication starts, the two strands of the original DNA are hydrogen-bonded together.
2. An enzyme unwinds and “unzips” the DNA
3. New complementary DNA nucleotides, which are always in the nucleus, fit into place by the process of complimentary base pairing. These position and are then joined by the enzyme DNA polymerase.
4. To complete replication, an enzyme seals any breaks in the sugar-phosphate backbone
5. The two double-helix molecules are identical to each other and the original DNA.

This general overview of DNA replication is from fig.cox.miami.edu.

RNA

Now for an RNA structure. We now know that DNA is made up of the A,T,G, and, C nucleotides. RNA, on the other hand, is made up of C,G,A, an U nucleotides. RNA is also single stranded. There are also three types of RNA. Let’s explore them. (Below is an RNA image from www.jncasr.ac.in)

The first is Ribosomal RNA or rRNA. It is produced in the nucleolus and its main job is to join with proteins made in the cytoplasm to form the subunits of ribosomes.

(This image comes from www.biocrawler.com)

Next up is Messenger RNA or mRNA. This is made in the nucleus, as opposed to the nucleolus. mRNA carries genetic information from DNA to the ribosomes in the cytoplasm.

(This image is from http://www.cofc.edu/~deavorj/102/notes/biochem/jpdnucla.html)

Lastly, you will find Transfer RNA or tRNA. This structure is also made in the nucleus. tRNA transfers amino acids to the ribosomes.

(Last but not least is this image from www.kensbiorefs.com)

All of these help form a protein.