Replication, Transcription, and Translation

Replication Where does replication occur in eukaryotes? Nucleus! In what phase does DNA replication occur? The S phase of Interphase! What are the basic building blocks of DNA? Nucleotides!

The Beginning Replication Fork Replication begins at the Origin of Replication As the two strands are opened, a Replication Fork is created. The new strand of DNA is created at the replication fork.

The Replication Fork The enzyme, Helicase is responsible for unwinding the double-stranded DNA

Replication Nucleotides are added to the open strands of DNA by an enzyme called DNA Polymerase Before DNA polymerase build the nucleotides together, there must be a primer o Primase- This enzyme creates the RNA primers that are needed for replication to begin DNA Polymerase can only add nucleotides in single direction. This causes there to be a leading strand and a lagging strand.

Replication

Leading Strand Continuously constructed as a single strand from the origin of replication to the replication fork

Lagging Strand Created from the replication fork to the origin of replication in many small fragments called Okazaki Fragments

Lagging Strand These Okazaki Fragments are connected by an enzyme o DNA Ligase DNA Ligase connects the Okazaki Fragments, completing the lagging strand

Semiconservative Model of Replication Idea presented by Watson & Crick The two strands of the parental molecule separate, and each acts as a template for a new complementary strand New DNA consists of 1 PARENTAL (original) and 1 NEW strand of DNA

Putting It Together

Now Answer This What enzyme is used to create the RNA primers? What is an Okazaki Fragment? Why is DNA Ligase important? Why is it important that replication be closely regulated?

Look Familiar? DNARNA NameDeoxyribonucleic AcidRibonucleic Acid SugarDeoxyriboseRibose StrandedDoubleSingle BasesA,T,C,GA,U,C,G Different BaseThymineUracil

Types of RNAs Messenger RNA (mRNA) o These are the “messages” that come from the DNA that must be read to make proteins o This message is read by codons A codon is the combination of THREE nitrogen bases C G A A

Types of RNAs Transfer RNA (tRNA) o These RNA are important for taking an amino acid to the ribosome during translation o Has 2 regions An amino acid is attached The anticodon o This allows the tRNA to attach to the mRNA and deliver the amino acid Amino Acid Region

Types of RNAs Ribosomal RNA (rRNA) o This RNA is used to build Ribosomes o Helps to translate mRNAs

Transcription: Some Facts The making of RNA from a DNA template o Uses DNA like a “script” to make RNA This process occurs in the nucleus for Eukaryotes and in the cytoplasm for Prokaryotes

Transcription Vocabulary Template Strand o The strand of DNA being copied Coding Strand or Non-template Strand o The RNA will look identical to this strand except Uracil will be substituted for Thymine Different Enzymes o Helicase o RNA polymerase - Adds the nucleotides to create the strand of mRNA.

Transcription The DNA is opened by the enzyme helicase to allow for the RNA to be created

Transcription The RNA polymerase adds bases in a continuous motion along the template strand

Transcription The enzymes continue to move down the template strand until the end of the gene

Transcription The mRNA is transported out of the nucleus to the ribosomes

This Begins the Process of Translation

Translation Facts This is the process of making a protein from mRNA o The ribosome “translates” the mRNA to a protein Proteins are required for the structure, function, and regulation of the body’s tissues and organs

Translation Vocabulary Amino Acid - The basic building blocks of a protein Peptide Bond- This is the specific bond formed between amino acids Polypeptide Chain - This is created by the adding of amino acids

The “Genetic Code” For every amino acid there is a matching codon o Since there are only 20 Amino acids, many have several codons that code for them

Translation The mRNA is taken into by a Ribosome Ribosome

Translation tRNAs bring the appropriate amino acid to the ribosome

Translation The anticodon region of the tRNA pairs with the codon of the mRNA

Translation The amino acids form a peptide bond.

Translation When the peptide bond is formed, the tRNA is removed from the ribosome

Translation The polypeptide chain is created by the forming of peptide bonds by the amino acids Growing polypeptide chain

Translation Amino Acids are continuously added until the ribosome “reads” the entire mRNA

Translation When the mRNA is completely translated, The peptide chain is released from the ribosome Met Val Ser Glu Ala Pro

Now You Try! Using this strand of DNA: 5’-ATGAGTCGGCCCTAGTGA-3’ Tell me the opposite strand of DNA, the template strand of DNA, the coding strand of DNA, the created mRNA, and the final chain of amino acids.

Answers Coding Strand 5’-ATGAGTCGGCCCTAGTGA-3’ 3’-TACTCAGCCGGGATCACT-5’ Template Strand mRNA 5’-UACUCAGCCGGGAUGAGU-3’ Amino Acid Chain Met-Ser-Arg-Pro-Tyr-STOP

Central Dogma of Biology