Protein Synthesis

Sarah Khan
Bivins-5th
April 20th, 2013

Protein Synthesis

Every day, you take in an abundance of different biomolecules; one of them being proteins. Have you ever wondered how proteins are made? They don't just grow from a tree or fall from the sky, they are made through a process called protein synthesis. Protein synthesis is broken up in two two steps: transcription and translation. Transcription starts inside the nucleus when the DNA is unzipped by helicase. Following that, the mRNA nucleotides match to their complementary bases using an enzyme called RNA polymerase. Once they are matched, the mRNA exits the nucleus and goes to a ribosome in the cytoplasm to begin translation. Translation is the synthesis of a protein using the genetic information encoded in the mRNA. Translation begins when the mRNA start codon, AUG, is placed at the ribosome P site. Once this has occurs, tRNA matches the amino acid Methionine to the codon using an anticodon- (UAC). tRNA then carries the next matching amino acid to the "A" site where a peptide bond forms between the two amino acids allowing a chain to form. The ribosome sifts one codon in the 3’ position so the next tRNA can match the codon to its amino acids for the building of another protien. Translation ends when the ribosome reaches a stop codon and an amino acid sequence, or a protein, is made. To find the original traits, I found six start codons (TAC) and six stop codons that did not overlap with other codons. I then labeled each gene from A through F and transcribed the genes to mRNA. Once transcribed, I translated mRNA to an amino acid chain forming from what each of the codons coded for. Then, using the sheet with the traits with corresponding amino acid chains, I found the original traits. The original traits were: wavy hair, blue eyes, pug nose, full lips, red hair, and oval face. A mutation is a change in the DNA sequence that changes the protein produced. There are point or frame-shift mutations. A point mutation is a simple change in one base of the gene sequence where you do not have an extra or one less nucleotide at the end of the sequence. Types of point mutations are substitution and inversion mutations. Frame-shit mutations are mutations that cause an extra or one less of a nucleotide to be at the end of the sequence. Types of frame-shift include deletion and insertion mutations. The mutations that each of gene E and gene B were both point substitution mutations. In gene E, changing the cytosine in the codon TCG to another guanine making it TGG caused the end result to have the gene expressed as blonde hair instead of red hair. In gene B, changing the adenine to a cytosine (AGA→CGA) affected the individual by changing the eye color from blue to hazel in the mutation. DNA determines traits by coding for certain sequences of amino acids that code for specific trait expression. Mutations increase the variation in species by allowing different kinds of genes to be expressed. For example, if 10 people in a room all had the same sequence of amino acids for a gene that expressed blue eyes, there is no variation. However, if 4 out of the 10 people each had a mutation, there would be a difference in eye color. Changing DNA affects the phenotype of a person. When you change DNA, you change the amino acid it codes for, which then changes the sequence of amino acids, which then changes what is expressed on the organism.