12-3: RNA AND PROTEIN SYNTHESIS Biology 2

DNA double helix structure explains how DNA can be copied, but not how genes work GENES: sequence of DNA that codes for a protein and thus determines a trait DNA must copy messages onto RNA RNA contains “codes” for making proteins Introduction

RNA is made of building blocks called nucleotides NUCLEOTIDES: monomer of nucleic acids made up of a 5- carbon sugar, a phosphate group, and a nitrogenous base Can have 4 different types of base: – Adenine – Guanine – Uracil (replaces Thymine) – Cytosine Structure of RNA Ribose Sugar

Backbone of RNA is sugar and phosphate groups – FORM THE OUTSIDE Bases DO NOT bond together to connect inside Components and Structure of DNA

1.DNA uses deoxyribose – RNA uses ribose sugar in nucleotides 2.DNA is double stranded – RNA is single stranded 3.DNA uses Thymine – RNA uses Uracil Differences Between RNA and DNA

3 types of RNA: mRNA: carries messages to ribosomes tRNA: transfers amino acids to the ribosomes rRNA: make up different parts of the ribosome Types of RNA

TRANSCRIPTION: process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA DNA creates a temporary copy of messages on mRNA, its carried to ribosomes and tRNA carries amino acids for building the proteins Transcription

During transcription enzyme attaches to PROMOTER sequence (like a green light) Enzyme will read all bases on a DNA strand to make mRNA message Enzyme will stop at TERMINATOR sequence (like a red light) Transcription

Proteins are made by joining amino acids into long chains – 20 different amino acids possible Properties of proteins are determined by sequence (order) of amino acids The message mRNA carries is called the Genetic Code The Genetic Code

Each set of 3 bases on mRNA is known as a codon – CODON: three-nucleotide sequence on messenger RNA that codes for a single amino acid Each codon has instructions for specific amino acid – Can have more than 1 codon for each amino acid The Genetic Code

Sequence (order) of bases in mRNA are instructions for which amino acids should be joined in a specific order Creating the chain of amino acids is called translation – TRANSLATION: decoding of a mRNA message into a polypeptide chain This is reading the mRNA message to figure out the order of amino acids Translation

Enzyme will read all bases on a DNA strand to make mRNA message – mRNA message is sent to ribosomes Ribosomes “read” the message tRNA carries the amino acids anti-codon matching the mRNA codon message to the ribosome Ribosome “glues” amino acids together to form protein chains Translation

Protein Synthesis – Translation Process

Bill Nye – Genes and Chromosomes