Chapter 13.1: RNA Essential Questions How does RNA differ from DNA? How does the cell make RNA?

The Structure of RNA RNA (Ribonucleic Acid) Single stranded chain of nucleotides 5 carbon sugar = ribose Phosphate group Nitrogenous bases Adenine Guanine Cytosine Uracil (No Thymine)

Genes and Proteins: Proteins = Many Amino Acids Proteins and Traits Proteins are involved in many cell functions Proteins help determine traits. Gene is a segment of DNA that specifies the amino acid sequence of a protein. Amino Acid = 3 nucleotide bases

The Role of RNA = Protein Synthesis Genes contain coded DNA instructions that tell cells how to build proteins. RNA serves as a temporary copy of DNA that translates this code into a protein.

Comparing RNA and DNA RNA Single stranded Sugar = Ribose Nitrogenous base uracil instead of thymine Double stranded Sugar = Deoxyribose Nitrogenous base thymine instead of uracil

The DNA molecule is organized into segments called genes.

You may have heard of genes You may have heard of genes. They contain the information needed to build proteins which do much of the work in our bodies. Each gene codes for a different type of protein. Optional: Let’s take a look at how a protein is made. Open the How Proteins Are Made animation on the next slide.

As you just saw in the animation, proteins are responsible for carrying out specific functions. They might be responsible for breaking down the food we eat, making our muscles contract or keeping our skin tight.

Types of RNA

From DNA to RNA to Protein Transcription A gene is copied into RNA using an enzyme called RNA polymerase. This copy is called messenger RNA (mRNA). Location: NUCLEUS mRNA then leaves the nucleus then moves onto a ribosome in the cytoplasm. A ribosome (rRNA) uses mRNA, tRNA, and amino acids to make proteins.

How Does it Work? RNA Polymerase: binds to region on the DNA known as a promoter, and begins transcription.

RNA Editing (splicing) Introns - which are not expressed Exons - expressed genes. Introns allow exons to be put together in various sequences so that different mRNA sequences can result from a single gene. Important for gene expression during cell differentiation and evolution.

The Genetic Code This is the language of mRNA Based on the 4 bases of mRNA (A,C,G,U) 3 bases = 1 codon The strand AUGAACUCU

The Genetic Code 3 nucleotide bases code for 1 Amino Acid Example: AAA = Lysine, CGU = Arginine, UCG = Serine, CCC = Proline

Translating the Genetic Code

Translation: mRNA  Protein Transcription: occurs in nucleus mRNA: Nucleus  cytoplasm  ribosomes tRNA: carry’s the amino acid to the ribosome Ribosomes: attach amino acids together forming a polypeptide chain Polypeptide chain grows until a stop codon is reached

Steps in Translation (Decoding mRNA) Start and Stop Codons Methionine AUG is the start codon There are 3 different stop codons mRNA is transcribed in the nucleus and enters the cytoplasm for translation

Steps in Translation Ribosome attaches to mRNA Each codon of mRNA directs tRNA to bring the specified amino acid into the ribosome One at a time, the ribosome then attaches each amino acid to the growing chain

Steps in Translation Each tRNA molecule has 3 unpaired bases called the anticodon that match to the mRNA codon. The tRNA molecule for methionine has the anticodon UAC, which pairs with the methionine codon, AUG. mRNA moves across the ribosome like a conveyor belt adding amino acids as it goes along, creating a chain of amino acids (polypeptide)

Steps in Translation The polypeptide chain continues to grow until the ribosome reaches a “stop” codon on the mRNA molecule. When the ribosome reaches a stop codon, it releases both the newly formed polypeptide (protein) and the mRNA molecule, completing the process of translation.

The Central Dogma of Molecular Biology DNA  RNA  PROTEIN

Central Dogma of Molecular Biology