foothill high school science department chapter 12 dna & rna section 12-2 chromosomes & dna...
TRANSCRIPT
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
Chapter 12DNA & RNA
Section 12-2Section 12-2Chromosomes &Chromosomes &DNA ReplicationDNA Replication
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
• DNA LocationDNA Location– Prokaryotes – CytoplasmProkaryotes – Cytoplasm
• Single Circular MoleculeSingle Circular Molecule
– Eukaryotes – NucleusEukaryotes – Nucleus• Multiple ChromosomesMultiple Chromosomes
– Humans 46Humans 46– Drosophila 8Drosophila 8– Giant Sequoia 22Giant Sequoia 22
DNA & Chromosomes
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
• E. coli (E. coli (Gram Neg. BacilliGram Neg. Bacilli))4,639,221 Base Pairs4,639,221 Base Pairs
1.6 mm long which must 1.6 mm long which must fit in a bacteria 1.6 um fit in a bacteria 1.6 um wide, or 1/1000 the wide, or 1/1000 the length of the DNA strandlength of the DNA strand
• Human DNA 1000 times Human DNA 1000 times largerlarger
• Tightly PackedTightly Packed
DNA Length
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
Chromosome Structure
Each Human Cell Contains More Each Human Cell Contains More Than A Than A 6 feet6 feet of DNA of DNA
• Tightly Packed Into Tightly Packed Into ChromatinChromatinDNA + Protein = DNA + Protein = ChromatinChromatinDNA Coiled Around Proteins Called DNA Coiled Around Proteins Called
HistonesHistones–Forms Beads Called Forms Beads Called NucleosomesNucleosomes
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
Chromosome Structure
• NucleosomesNucleosomes pack together to form a thick pack together to form a thick fiber containing loops and curlsfiber containing loops and curls
Usually loose, diffuseUsually loose, diffuseCondense during Mitosis & MeiosisCondense during Mitosis & Meiosis
Fold enormous lengths of DNA into the tiny nucleusFold enormous lengths of DNA into the tiny nucleus
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
Chromosome Structure
HistonesHistones
proteins that have very proteins that have very low mutation rateslow mutation rates
Appears most mutations Appears most mutations have been lethal – have been lethal – therefore, eliminatedtherefore, eliminated
Regulate “reading” of Regulate “reading” of chromosomechromosome
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
DNA Replication
• Watson & Crick Watson & Crick DiscoveredDiscovered– Structure of DNAStructure of DNA– How DNA can be copied How DNA can be copied
& replicated.& replicated.– Each strand of DNA is a Each strand of DNA is a
mirror image of the other mirror image of the other strandstrand• Strands areStrands are
ComplimentaryComplimentary
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
Duplicating DNA
ReplicationReplicationDuplication of the DNA in preparation for cell Duplication of the DNA in preparation for cell
division ( S phase of Interphase )division ( S phase of Interphase )
ProkaryotesProkaryotesReplication starts at a single point and proceeds in Replication starts at a single point and proceeds in
opposite directionsopposite directions
EukaryotesEukaryotesOccurs at multiple points on multiple chromosomes Occurs at multiple points on multiple chromosomes
at onceat once
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
Duplicating DNA
Key ConceptKey Concept::During DNA replication, the DNA During DNA replication, the DNA
molecule separates into two strands, molecule separates into two strands, then produces two new then produces two new complementary strands following the complementary strands following the rules of base pairing. Each strand of rules of base pairing. Each strand of the double helix of DNA serves as a the double helix of DNA serves as a template, or model, for the new template, or model, for the new strandstrand
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
How Replication Occurs
Carried out by enzymesCarried out by enzymes1)1) They unzip the molecule of DNAThey unzip the molecule of DNA
Break the hydrogen bonds between the Break the hydrogen bonds between the base pairsbase pairs
2)2) Each strand is a template for the new Each strand is a template for the new strandstrand
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
DNA Replication
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
How Replication Occurs
• Original DNAOriginal DNA
TACGTTTACGTT
ATGCAAATGCAA
• Unzipped Unzipped
TACGTT TACGTT ATGCAAATGCAA
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
How Replication Occurs
Replicated:Replicated:
TACGTT TACGTT ATGCAAATGCAA
ATGCAA TACGTTATGCAA TACGTT
Remember – Base PairingRemember – Base Pairing
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
How Replication Occurs
Enzymes Involved Named For The Enzymes Involved Named For The Reactions They CatalyzeReactions They Catalyze
DNA PolymeraseDNA Polymerase1)1) Polymerizes individual nucleotidesPolymerizes individual nucleotides
2)2) Proof Reads each new DNA strandProof Reads each new DNA strand
FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT
DNA Polymerase