DNA, RNA & PROTEIN SYNTHESIS FROM GENE TO PROTEIN

DNA DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell. We study DNA for many reasons: its importance to all life on Earth, it makes up every living organism, and it enables us to better engineer crops.

Our genes are on our chromosomes. Every human somatic cell should have 46 chromosomes. The shape of DNA is called a double helix because it is like a twisted ladder. The scientists, Watson and Crick are credited with the discovery that DNA has this structure. All DNA molecules are composed of nucleotides.

The backbone of the molecule is made of alternating sugars and phosphates, while the steps of the ladder are made of nitrogenous base pairs. DNA has four different bases: Adenine, Thymine, Cytosine, and Guanine. Thymine and Cytosine are called pyrimidines, which have single rings. Adenine and Guanine are called purines, which are double ring bases.

These bases attract to each other because of hydrogen bonding. These bonds are weak, but there are millions of them in a single molecule of DNA. When making hydrogen bonds, Adenine always pairs with thymine and cytosine always pairs with guanine.

Chargaff’s Rule states that the amounts of Adenine and Thymine are equal and the amounts of Cytosine and Guanine are equal in a given molecule of DNA because of the pairing between them. Each cell has about 2 meters length of DNA. The average human has 30 trillion cells. Therefore, the average human has enough DNA to go from the earth to the sun more than 400 times.

RNA RNA stands for ribonucleic acid. RNA is made from DNA, and is single-stranded instead of double-stranded. RNA has four nitrogenous bases as well, but one is different.  Adenine, Cytosine, Guanine, and Uracil

There are three types of RNA: mRNA (messenger RNA), rRNA (ribosomal RNA), and tRNA (transfer RNA)

PROTEIN SYNTHESIS DNA begins the process called Protein Synthesis, which is also known as the Central Dogma of biology. This process has three steps:  DNA Replication  Transcription  Translation

REPLICATION DNA is constantly replicating in the nucleus of the cell. This has to happen in order for protein synthesis to begin. DNA replicates with the help of an enzyme called DNA Polymerase. Proteins are assembled at the ribosomes, which are found in the cytoplasm. DNA cannot leave the nucleus, so step 2—Transcription has to occur.

DNA goes through transcription in order to make mRNA. mRNA can leave the nucleus and goes out to the ribosomes. Translation is the final part of the process. After rRNA has read the message from mRNA, tRNA pairs the correct amino acid with each section of three bases on the mRNA strand. These sections of three are called codons.

The tRNA will keep pairing amino acids until it reaches a stop codon, which says that the protein is finished. Think of protein synthesis as the workings of a factory: the nucleus would be the boss’s office, and the DNA would be the boss himself. The boss (DNA) gives instructions for making the product to a messenger (mRNA) and that messenger takes the instructions to the floor. The workers read the instructions and begin to assemble (tRNA) the product (protein).