1. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Chapter 12 DNA & RNA Section 12-2 Chromosomes & DNA Replication

2. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT DNA LocationDNA Location –Prokaryotes – Cytoplasm Single Circular MoleculeSingle Circular Molecule –Eukaryotes – Nucleus Multiple ChromosomesMultiple Chromosomes –Humans 46 –Drosophila 8 –Giant Sequoia 22 DNA & Chromosomes

3. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT E. coli ( Gram Neg. Bacilli )E. coli ( Gram Neg. Bacilli ) 4,639,221 Base Pairs 1.6 mm long which must fit in a bacteria 1.6 um wide, or 1/1000 the length of the DNA strand Human DNA 1000 times largerHuman DNA 1000 times larger Tightly PackedTightly Packed DNA Length

4. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Chromosome Structure Each Human Cell Contains More Than A 6 feet of DNA Tightly Packed Into ChromatinTightly Packed Into Chromatin DNA + Protein = Chromatin DNA Coiled Around Proteins Called Histones –Forms Beads Called Nucleosomes

5. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Chromosome Structure Nucleosomes pack together to form a thick fiber containing loops and curlsNucleosomes pack together to form a thick fiber containing loops and curls Usually loose, diffuse Condense during Mitosis & Meiosis Fold enormous lengths of DNA into the tiny nucleus

6. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Chromosome Structure Histones proteins that have very low mutation rates Appears most mutations have been lethal – therefore, eliminated Regulate “reading” of chromosome

7. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT DNA Replication Watson & Crick DiscoveredWatson & Crick Discovered –Structure of DNA –How DNA can be copied & replicated. –Each strand of DNA is a mirror image of the other strand Strands are ComplimentaryStrands are Complimentary

8. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Duplicating DNA Replication Duplication of the DNA in preparation for cell division ( S phase of Interphase ) Prokaryotes Replication starts at a single point and proceeds in opposite directions Eukaryotes Occurs at multiple points on multiple chromosomes at once

9. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Duplicating DNA Key Concept: During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template, or model, for the new strand

10. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT How Replication Occurs Carried out by enzymes 1)They unzip the molecule of DNA Break the hydrogen bonds between the base pairs 2)Each strand is a template for the new strand

11. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT DNA Replication

12. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT How Replication Occurs Original DNAOriginal DNATACGTTATGCAA UnzippedUnzipped TACGTT ATGCAA

13. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT How Replication Occurs Replicated: TACGTT ATGCAA ATGCAA TACGTT Remember – Base Pairing

14. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT How Replication Occurs Enzymes Involved Named For The Reactions They Catalyze DNA Polymerase 1)Polymerizes individual nucleotides 2)Proof Reads each new DNA strand

15. FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT DNA Polymerase