Quick Write: Be in your seat before the bell rings. Begin your quick write: What is a gene? What does it code for?

DNA Replication & Expression How does DNA code actually create physical traits?

DNA replication DNA replication – the process of making a copy of DNA Understanding how DNA is copied has led to a better understanding of genetic diseases and cancer

Steps of Replication Step 1: Unwinding and separating DNA strands DNA Helicase – An enzyme that unwinds the DNA double helix during DNA replication

Steps of Replication Step 2: Adding complementary bases DNA polymerase – an enzyme that catalyzes the formation of the DNA molecule

Steps of Replication Step 3: Formation of two identical DNA molecules

Replication Proteins During the replication of DNA, many proteins from a machinelike complex of moving parts

Replication Proteins During the replication of DNA, many proteins from a machinelike complex of moving parts DNA polymerases also have a “proofreading” function

Prokaryotes

Eukaryotes

Prokaryotes Prokaryotes have a single circular DNA molecule or chromosome Prokaryotes will have two replication forks that start at the same point

Eukaryotes Eukaryotes have several chromosomes Eukaryotes have linear DNA which also contains proteins which have many replication sites to increase the speed

Quick review Describe the steps of DNA replication Compare the roles of DNA helicase and DNA polymerases Compare the process of DNA replication in prokaryotes and in eukaryotes

Gene expression Gene expression – the manifestation of the genetic material of an organism in the form of specific traits Gene expression produces proteins by transcription and translation.

Gene expression

RNA review In cells, three types of RNA transcribe DNA and translate the genetic code into proteins mRNA – messenger RNA, carries instructions for making a protein from a gene tRNA – transfer RNA, “reads” the mRNA sequence and translates the mRNA into a specific sequence of protein subunits, or amino acids rRNA – ribosomal RNA, the RNA that makes up ribosomes

Central Dogma: DNA to RNA to Protein (5' -> 3') ATG GAA TTC TCG CTC (Coding strand) DNA (3' <- 5') TAC CTT AAG AGC GAG (Template strand) DNA (5' -> 3') AUG GAA UUC UCG CUC (mRNA) (contains codons) (3' <- 5') UAC CUU AAG AGC GAG (tRNA) (contains anticodons) Transcription Translation Protein

Transcription Transcription – the process of forming a nucleic acid by using another molecule as a template Transcribe…… Scribe? Transcription is DNA to RNA DNA RNA

Steps of Transcription Step 1: RNA polymerase binds to the DNA promoter, or start site

Steps of Transcription Step 2: The two strands unwind and separate to expose the DNA

Steps of Transcription Step 3: RNA polymerase adds the complementary RNA bases

Transcription vs Replication Replication? When DNA duplicates to make more DNA Transcription? When DNA is used to make RNA Both use DNA as the template, but they have different results

Review codons and UGC Codons in mRNA

Review codons and UGC Codons in mRNA GGAAUGCAAAGCGAU

Translation Translation – the portion of protein synthesis that takes place at ribosomes and that uses the codons in mRNA molecules to specify the sequence of amino acids in polypeptide chains Basically: during translation amino acids are assembled from information encoded in mRNA Translate?

Translation

RNAProtein RNA Translation

Steps of Translation Step 1: The ribosome, mRNA, and tRNA which is carrying the amino acid methionine bind together Step 2: A new tRNA arrives and binds to the next codon on the mRNA. A peptide bond forms between the first amino acid and the amino acid created by this tRNA

Translation – RNA into Proteins

Steps of Translation The anticodon from the tRNA matches with the codon from the mRNA Anticodon – is complementary to the mRNA codon

Steps of Translation Step 3: the first tRNA detaches and leaves its amino acid. With each new tRNA, the amino acid chain grows Step 4: the process ends when a stop codon is reached Step 5: the amino acid chain is released, and the ribosome complex falls apart

Steps of Translation

Review Replication? DNA makes more DNA Transcription? DNA makes RNA Translation? RNA makes Protein

Overview

Mutations