RNA & Protein Synthesis
DNA, RNA, & Proteins Genes: coded instructions for making protein. RNA is made from DNA. RNA contains the information to make proteins.
RNA DNA Ribose Sugar Single Strand Uracil (U) RNA: a disposable copy of a DNA segment. a working copy of a single gene. Deoxyribose Sugar Double Strand Thymine (T)
Types of RNA Messenger RNA (mRNA): carries a copy of the instructions to make proteins. Ribosomal RNA (rRNA): makes up the ribosome, where proteins are made. Transfer RNA (tRNA): transfers amino acids to the ribosome.
Transcription The process of copying part of the DNA to mRNA. Occurs in the nucleus. The DNA strands separate. One strand of DNA is used as template for RNA. A stop signal is reached when a RNA molecule is complete.
Transcription
RNA Editing DNA contains: Introns: region not involved in proteins Exons: expressed in proteins In forming RNA, introns & exons are included. In the nucleus, introns are cut out. The remaining exons are spliced together to form the final mRNA.
The Genetic Code Proteins are made of chains of amino acids. The order of amino acids is determined by order of the mRNA bases. The mRNA is divided into three letter sections called codons. Each codon specifies a specific amino acid.
Codon Sequence Consider the mRNA sequence: UCGCACGGU It can be read three bases at a time: UCG-CAC-GGU The codons represent different amino acids: Ser-His-Gly
Codons Because there are 4 different bases, there are 64 possible codons. But there are only 20 amino acids? Some codons code for several amino acids. The codon, AUG, represents Met, the only start codon. There are three stop codons.
Translation The cell uses mRNA to make proteins. Occurs in ribosomes. A ribosome is like a factory that puts the amino acids together. Translating English to Russian.
Translation
DNA to Amino Acid DNA: AGC-GTG-CCA mRNA: UCG-CAC-GGU tRNA: AGC-GUG-CCA Amino Acid: Ser-His-Gly The mRNA is used to determine the amino acids, not the tRNA.
Role of DNA and RNA DNA is like the master plan for a construction job. It is too dangerous to take it to the job site, so it stays in the main office, the nucleus. RNA acts like a blue print, or a disposable copy for the job. It’s safer to take the blueprint to the job site.
Why are proteins so important? Many proteins are enzymes, which catalyze and regulate chemical reactions. Proteins are tools used to operate every component of an organism.