Protein Synthesis

Protein synthesis is based on the central dogma. The central dogma is DNA-RNA-Proteins. Protein synthesis begins within the nucleus. It begins with the chromosomes. Chromosomes are made up of DNA wound around protein spools called histones.

DNA is made up of two strands. The two strands are complementary to one another. Each strand is made up of nucleotides and a deoxyribose back bone. There are four types of nucleotides: adenine, thymine, guanine, and cytosine. Guanine is complementary cytosine and thymine is complementary to adenine. These nucleotides are held together with hydrogen bonds. Adenine and thymine are held together by a double hydrogen bond, and guanine and cytosine are held together by a triple hydrogen bond. Sometimes there are mutations in DNA. These can either greatly change the traits of the animal, or they can have no difference at all.

Protein synthesis begins with a process called transcription. Transcription begins with the unwinding of histones and DNA. Then an enzyme called helicase starts a replication fork where the DNA begins to be unwound. This is the start signal region for the transcription from DNA into pre-mRNA. One of the strands of DNA is used as a template for the pre mRNA. When DNA is transcribed into mRNA the thymine is not transcribed into adenine it is transcribed into uracil. After the pre mRNA is finished being transcribed it begins to break into pieces. Then the premrna begins to reassemble to form finished mRNA. Pieces of the pre-mRNA called introns are left out. The mRNA is made up of codons .Since the DNA cannot leave the nucleus it sends the coded instructions on how to make the proteins via the finished mRNA. The mRNA leaves the nucleus through a nuclear pore.

The mRNA travels through the cytoplasm to the (RER) rough endoplasmic reticulum. The RER contains the ribosomes that the mRNA travels to. Mrna also travels to free floating ribosomes in the cytoplasm. Proteins are made in ribosomes. When the mRNA is at the ribosome it is met by a tRNA. The tRNA is made of anticodons. The anti-codons are complementary to specific codons on the mRNA. Thru tRNA carries an amino acid to the ribosome. Then the anti-codon of the tRNA meets with the start codon on the mRNA. The tRNA then waits for another tRNA to come so it can pass over its amino acid. When there is one bond between amino acids it is a peptide bond, when there is two bonds it is a dipeptide bond. Once there are more than three bonds