RNA Protein Synthesis DNA RNA Proteins Genes coded

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 • Ribose Sugar • Single Strand • Uracil (U) DNA • Deoxyribose Sugar • Double Strand • Thymine (T) • RNA: – a disposable copy of a DNA segment. – a working copy of a single gene.

Types of RNA • Messenger RNA (m. RNA): carries a copy of the instructions to make proteins. • Ribosomal RNA (r. RNA): makes up the ribosome, where proteins are made. • Transfer RNA (t. RNA): transfers amino acids to the ribosome.

Transcription • The process of copying part of the DNA to m. RNA. • 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 m. RNA.

The Genetic Code • Proteins are made of chains of amino acids. • The order of amino acids is determined by order of the m. RNA bases. • The m. RNA is divided into three letter sections called codons. • Each codon specifies a specific amino acid.

Codon Sequence Consider the m. RNA sequence: UCGCACGGU It can be read three bases at a time: UCG-CAC-GGU The codons represent different amino acids: UCG-CAC-GGU 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 m. RNA 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: m. RNA: t. RNA: Amino Acid: AGC-GTG-CCA UCG-CAC-GGU AGC-GUG-CCA Ser-His-Gly The m. RNA is used to determine the amino acids, not the t. RNA.

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.