DNA Replication and Protein Syntheses

What does DNA stand for? 2) What is the shape that DNA has? 3) What makes you unique and individualized from everyone else? 1) DNA -> RNA -> Protein   From DNA to Proteins 2 Types of nucleic acid Frederick Griffith – Experimented with two forms of bacteria that cause pneumonia on mice o Smooth (S) and Rough (R) o Demonstrated Transformation His conclusion: some factor changed the bacteria o “Transforming Principle”  Oswald Avery – Was puzzled by Griffith’s discovery and worked for 10 years to find the answer. o Directly observed transformation of R bacteria into S bacteria  Concluded that DNA is the transforming principle o DNA = Genetic material  Hershey and Chase- supported the conclusion - DNA is the source of genetic information o Used bacteriophage infected with radioactive sulfur atoms on protein. • Bacteriophage – a virus that infects and replicates within bacteria. • Minimal radioactivity found in bacteria o Used bacteriophage infected with radioactive phosphorus atoms on DNA. • Radioactivity found in bacteria     DNA DNA stands for Deoxyribo Nucleic Acid DNA is genetic material that determines inherited characteristics/traits The job of DNA is to code for proteins in the body.  What is the monomer that makes up DNA? o DNA is made up of long chains of Nucleotides. o Nucleotides- make up genes that code for a specific trait.  What makes up a Nucleotide? o 1. Deoxyribose sugar ( S ) o 2. Phosphate ( P ) o 3. Nitrogen Base • • • • Adenine (A) Guanine (G) Cytosine (C) Thymine (T) Nitrogen bases come in two types: 1. Adenine 2. Guanine Nitrogen bases come in two types: Pyrimidines have ONE ring   And come in two types: 1. Cytosine 2. Thymine   Double Helix – Spiral ladder o Discovered by Watson and Crick in the 1950’s with the help of Franklin’s x-ray pictures o Double stranded (Antiparallel) Complementary base paring – the nitrogen bases on one side of the ladder ALWAYS pair up with the same nitrogen base on the other side of 5’ 3’ the ladder. o Discovered by Chargaff o The pairs are held together with hydrogen bonds A→T G→C 5’ 3’ T P Complete the other side of the DNA molecule P A P P C P P C Circle a nucleotide P P T T A P Complete the other side of the DNA molecule P A T P P C G P P C Circle a nucleotide G P P T A  Remember: DNA is always copied during cell cycle o Mitosis & Meiosis  This takes place during the S phase of Interphase  1. The DNA molecule is split down the middle (at the nitrogen bases) by helicase, breaking the hydrogen bonds. o Similar to a zipper    2. The nitrogen bases on each side of the molecule are used as a pattern for a new strand. 3. Complementary bases are added to each individual strand by DNA polymerase (enzyme). Each new cell can now get a complete copy of all the DNA. – Semi-conservative o One of the original strand, one new DNA polymerase adds the new nucleotides one at a time. Lastly, DNA ligase enzyme “glues” nucleotides together on the lagging strand.  Both nucleotide chains separate and serve as a template for a new nucleotide chain.  The open structure is often referred to as a replication fork.  The leading strand requires fewer steps and therefore is synthesized more quickly.  The lagging strand is done in pieces since the helix uncoiling occurs in the opposite direction the polymerase is working. These pieces are called Okazaki fragments. ***You are left with 2 exactly identical molecules of DNA double helix.*** Original strands of DNA Original New New Original Semi-conservative Model O N N O  DNA → RNA → Protein Transcription DNA → RNA Translation RNA → Protein o Why make proteins? • Skin, muscles, nails, hair, hormones, enzymes • How do we make proteins? RNA is the 2nd type of Nucleic Acid  RNA is made of nucleotides, just like DNA  o 1. Ribose is the sugar o 2. Phosphate o 3. Nitrogen Bases • Adenine (A) • Guanine (G) • Cytosine (C) • Uracil (U): NOT Thymine (T) o Single Stranded o When RNA is assembled based off of DNA’s pattern, this is called Transcription Types: 1. mRNA – messenger 2. tRNA – transfer 3. rRNA - ribosomal Comparing DNA and RNA DNA RNA SUGAR Deoxyribose Ribose BASES A T C G A U C G Double Helix Single Stranded Nucleus Nucleus. Cytoplasm, Ribosomes STRUCTURE LOCATION    Occurs in the nucleus DNA is again unzipped by RNA Polymerase. RNA Polymerase adds complementary RNA nucleotides DNA is too large to get out of the nucleus, RNA carries DNA’s message out of the nucleus to a ribosome. Ribosome – where the protein will be made. o Starting at a region called the promoter o This makes mRNA o mRNA = messenger = carries the message  mRNA leaves the nucleus DNA Deoxyribose P Deoxyribose Adenine ---H--- Thymine Uracil mRNA DNA exits re-coils nucleus RNA RNAPolymerase Polymerase Strands move breaks makes apart H-bonds mRNA Cytosine ---H---Guanine Guanine Guanine P Deoxyribose Ribose Ribose Deoxy- ribose P P Ribose Ribose Deoxy- ribose P P Thymine ---H---Adenine Adenine Adenine P P Ribose Ribose Deoxy- ribose       DNA strand = AATTTGCGCGGCT mRNA strand = DNA strand = TATGCGCACTG mRNA strand = DNA strand = CGATCAGCCTAT mRNA strand =  Many RNA molecules require a bit of editing before they leave the nucleus.  Introns- not involved in coding for proteins o These get taken out  Exons- are expressed   RNA to Protein Translation converts mRNA messages into Polypeptides o String of amino acids held together by a peptide bond   A codon is a sequence of three nucleotides that codes for an amino acid. Examples: o AUG= Methionine o CUU= Leucine  The genetic code matches the mRNA codon with the tRNA anticodon to link amino acid or action AUG= Start/ Methionine UAA, UGA or UAG= Stop  Codon GCA =  Codon AAG =  Codon CGA =   Only 20 Amino Acids 1 START codon 3 STOP codons    mRNA carries the DNA instructions for making protein mRNA goes into the cytoplasm through nuclear pores mRNA attaches to a ribosome to be “read” o Ribosomal RNA (rRNA)   Appropriate amino acids are strung together to build a polypeptide chain by reading codons. Amino acids are attached to Transfer RNA (tRNA) o tRNA is complementary to mRNA o mRNA codon- ACC o tRNA anti-codon = o mRNA codon - GUC o tRNA anticodon =  Polypeptide chain = protein TRANSLATION Process of assembling polypeptides from information encoded in mRNA; Interpreting the code! Number the 4 anticodons in the order they occur 1. Which two mRNA codes correspond to histidine? 2. How many different mRNA codes correspond to arginine? There are two types of mutations o Sex cell mutations: affect the offspring o Body cell mutations: affect the individual only Most mutations cause a disorder or silent mutations DNA Polymerase can usually detect errors  Mistakes in base paring during DNA Replication o Cause of many genetic disorders o Gene Mutations (single gene) and Whole Chromosome (Chromosomal Mutations)  Chemicals: like tobacco o Can lead to cancer because it changes the genes that regulate mitosis  Radiation: including UV (sun) and X-ray o Can lead to cancer because it changes the genes that regulate mitosis  1. Substitution o Point where one nitrogen base is substituted for another o Sickle Cell Anemia: substitute A for T  2. Deletions and insertions o When a nitrogen base is deleted or added o Frame shift mutations- because it moves the codon up or down o Changes the sequence of amino acids