10Important Scientists in the “Race for the Double Helix” Maurice Wilkins & Rosalind FranklinX-ray diffractionDNA must be a some type of spiral (helix)DNA’s diameter is constant and stable
11DNA FACTS established by James Watson and Francis Crick Shape of a double helix
12What is a Gene? A length of DNA on a chromosome May be in several partsExon – the expressed parts of the DNA sequenceIntron – the intervening, “junk DNA”, not expressedParts are cut, put together and then used to make RNA and proteins
13DNA:codes for your genes (traits)made of repeating subunits called nucleotides
14What is a nucleotide? Has three parts: PHOSPHATE DEOXYRIBOSE (sugar) BASE (A,T,G,C)
15Base-Pair Rule Adenine <==> Thymine Guanine <==> Cytosine The sides of the DNA ladder are phosphate & sugarheld together by hydrogen bonds
16Base Pair RuleOne side: A T A T C A T G C G G GOther side:
18How the Code WorksThe combination of A,T,G,C determines what traits you might have, for ex.C A T C A T = purple hairT A C T A C = yellow hair
19Think of the bases of DNA like letters. Letters form words Think of the bases of DNA like letters. Letters form words.... Words form sentences.... *endless combinations
20Let's Review What We Know About DNA 1. DNA stands for: De _____ ribo ______ acid2. What is the shape of DNA? _______________3. Who established the structure of DNA? ____________4. Adenine always pairs with _______________5. The sides of the DNA ladder are deoxyribose and _____6. Guanine always pairs with _____________7. What is the complimentary sequence: A A T G C A8. The two sides of DNA are held together by _______ bonds.9. DNA is composed of repeating subunits called ______________________10. What are the 4 bases that make up the rungs of the DNA ladder? _______________________________________
22Replication Facts DNA has to be copied before a cell divides DNA is copied during the S or synthesis phase of interphaseNew cells will need identical DNA strands
23Synthesis Phase (S phase) S phase during interphase of the cell cycleNucleus of eukaryotesMitosis-prophase-metaphase-anaphase-telophaseG1G2SphaseinterphaseDNA replication takesplace in the S phase.
24DNA Replication Begins at Origins of Replication Two strands open forming Replication Forks (Y-shaped region)New strands grow at the forksReplicationForkParental DNA Molecule3’5’
25DNA ReplicationEnzyme Helicase unwinds and separates the 2 DNA strands by breaking the weak hydrogen bondsSingle-Strand Binding Proteins attach and keep the 2 DNA strands separated and untwisted
26DNA ReplicationBefore new DNA strands can form, there must be RNA primers present to start the addition of new nucleotidesPrimase is the enzyme that synthesizes the RNA PrimerDNA polymerase can then add the new nucleotides
27DNA REPLICATIONthe process by which DNA makes a copy of itself (cell division)SEMI-CONSERVATIVE - half of the old strand is saved
28DNA Replication Replication = Duplication Happens in the S phase of InterphaseMust replicate before mitosis or meiosis IPart of the double helix is unwoundReplication in small pieces (Okazaki fragments)Enzyme stitches pieces together later
30Structure of RNAGenes – are coded DNA instructions that control production of proteins.1. consists of a long chainof nucleotides (single strand))2. contains sugar ribose3. contains nitrogenous baseUracil
31Types of RNA Messenger RNA mRNA carries copies of instructions Ribosomal RNA rRNA found in ribosomeswhere proteins are made.Transfer RNA tRNA brings in amino acids tomake a protein.
32TranscriptionProcess in which a sequence of DNA is copied into a complementary sequence of RNARNA polymerase – enzyme used to open DNA strand and assemble a strand of RNA from DNA template.Promoters –regions of DNA that tells RNA polymerase where to start and stop.
36TranslationRibosomes – read instructions from mRNA and makes proteins (Decoding of mRNA)Translation begins when mRNA attaches to ribosomemRNA moves through ribosome 1 codon at a time.Codon is read and tRNA brings in the amino acid that is coded by that codon.*each tRNA carries only one kind of amino acid.*tRNA carries an anticodon that is complimentary to one mRNA codon.Another tRNA comes in with the next amino acid and then the ribosomes bind the AA with a peptide bond.The polypeptide chain grows until the ribosome reaches a stop codon. Then it releases the protein.