NOTES: CH 16 (part 2) – DNA Replication and Repair.

Slides:



Advertisements
Similar presentations
Chapter 6 DNA  Consists of Deoxyribose sugar Phosphate group A, T, C, G  Double stranded molecule (Double Helix) Two strands of DNA run antiparallel.
Advertisements

Chapter 11: DNA and Its Role in Heredity Exit Next Previous Home Discussion topics Chapter summaries CHAPTER 11 DNA and Its Role in Heredity.
DNA Replication.
AP Biology Chapter 16 part 2
DNA, AND IN SOME CASES RNA, IS THE PRIMARY SOURCE OF HERITABLE INFORMATION Genetic information is transmitted from one generation to the next through DNA.
Nucleic Acids and DNA Replication. 1. What is the role of nucleic acid? 2. What is the monomer of a nucleic acid? 3. The monomer of a nucleic acid is.
DNA Timeline to the discovery of DNA: 1928 – Fredrick Griffith discovers non-virulent bacteria (Streptococcus pneumoniae) become virulent when in contact.
CHAPTER 16 THE MOLECULE BASIS OF INHERITANCE Section B: DNA Replication and Repair 1.During DNA replication, base pairing enables existing DNA strands.
DNA Replication: A Closer Look
Unit 9: The Central Dogma Honors Biology.  The process of DNA replication is fundamentally similar for prokaryotes and eukaryotes.  DNA replication.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Basic Principle: Base Pairing to a Template Strand Since the two strands of.
The MOLECULAR BASIS OF INHERITANCE
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings.
DNA, AND IN SOME CASES RNA, IS THE PRIMARY SOURCE OF HERITABLE INFORMATION Genetic information is transmitted from one generation to the next through DNA.
DNA- The "Stuff" of Life Its replication and its unending repair.
THE MOLECULAR BASIS OF INHERITANCE
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings DNA Replication chapter 16 continue DNA Replication a closer look p.300 DNA: Origins.
DNA Replication Lecture 7. DNA Replication  Synthesis of two new DNA duplexes based on complementary base sequences with parental DNA.  Is progressive,
Frederick Griffith uncovered genetic role of DNA Transformation- change in genotype and phenotype due to assimilation of external DNA by a cell Pathogenicity.
Genetics DNA Replication Genetics Why do cells divide…  for reproduction  One celled organisms (clones)  for growth & development  From.
AP Biology Synthesis of DNA June
16.2 DNA Replication. DNA in Prokaryotes and Eukaryotes Prokaryotes: –ring of chromosome –holds nearly all of the cell’s genetic material.
DNA Structure & Replication AP Biology. What is a Nucleotide?
REVIEW DNA Structure. Deoxyribonucleic Acid DNA Deoxyribose sugar Double helix A -2-T, C-3-G Strands are complementary Purines: A and G Pyrimidines: T.
THE MOLECULAR BASIS OF INHERITANCE Chapter 16. THE SEARCH FOR GENETIC MATERIAL Frederick Griffith (1928) – something changed normal cells into pneumonia.
AP Biology DNA Replication AP Biology Watson and Crick 1953 article in Nature.
The Molecular Basis of Heredity Chapter 16. Learning Target 1 I can explain why researchers originally thought protein was the genetic material.
16.2 DNA Replication.
DNA REPLICATION SBI4U Ms. Manning. DNA Replication  Produces two identical copies of the chromosome during S phase of interphase  Catalyzed by many.
Beyond Mendel - the molecular basis of inheritance, and DNA biology 1.
DNA Replication.
DNA Replication IB Biology HL 1 Mrs. Peters Spring 2014.
Do Now!!  Why must DNA be replicated?  Where do you think replication takes place?  Are mistakes ever made while replicating DNA?  Why must DNA be.
DNA REPLICATION TOPIC 3.4 & 7.2. Assessment Statements Explain DNA replication in terms of unwinding the double helix and separation of the strands.
DNA Replication during cell division in eukaryotic cells, the replicated genetic material is divided equally between two daughter cells. it is important.
Chapter 16 DNA REPLICATION. REVIEW: HISTORY & STRUCTURE.
DNA Replication Copying DNA Replication of DNA – base pairing – new strand is 1/2 parent template & 1/2 new DNA semi-conservative copy process.
CHAPTER 16 THE MOLECULE BASIS OF INHERITANCE Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section B: DNA Replication and Repair.
Maurice Wilkins and Rosalind Franklin: X-ray crystallography DNA was helical in shape and the width of the helix was discovered (2nm). Copyright © 2002.
AP Biology DNA Replication AP Biology Watson and Crick 1953 article in Nature.
DNA Replication Lecture 11 Fall Read pgs
DNA Replication Ch 16 Unit Test: Ch
REVIEW ON ORGANIC MOLECULES NUCLEOTIDES, THE MONOMERS OF NUCLEIC ACIDS (DNA, RNA) ARE MADE OF 3 SMALLER MOLECULAR BUILDING BLOCKS: –A NITROGENOUS BASE.
7.2 DNA Replication Assessment Statements: I know that DNA replication occurs in a 5’ 3’ direction. I can explain the process of DNA replication in prokaryotes.
DNA REPLICATION C T A A T C G GC A CG A T A T AT T A C T A 0.34 nm 3.4 nm (a) Key features of DNA structure G 1 nm G (c) Space-filling model T.
Molecular Basis of Inheritance. DNA Studies Frederick Griffith – 1928 Frederick Griffith Streptococcus pneumoniae 2 strains – pathogenic & harmless Killed.
It takes E. coli less than an hour to copy each of the 5 million base pairs in its single chromosome and divide to form two identical daughter cells. A.
DNA: The Molecule of Heredity Chemical nature of DNA –Chromosomes are composed of protein and deoxyribonucleic acid –Gene – functional segment of DNA located.
1.DNA MOLECULES ARE LONG POLYMERS MADE UP OF REPEATING NUCLEOTIDES.
Chapter 16.2 DNA Replication and Repair. Recap Nitrogen base pairings A – T C – G Adenine and Guanine are purines -2 rings Cytosine and Thymine are pyrimidines.
DNA Replication.
Do Now  What is replication?  Where does this take place?
DNA Replication How does each cell have the same DNA? How is a prokaryote different than a eukaryote?
DNA Replication the big event during S phase. The Animation hill.com/sites/ /student_view0/chapter14/animations.html#
General Animal Biology
DNA REPLICATION.
copyright cmassengale
DNA Replication.
DNA Replication.
DNA Replication.
5 end 3 end 3 end 5 end Hydrogen bond 3.4 nm 1 nm 0.34 nm (a)
Chapter 13 DNA Replication.
Deoxyribonucleic Acid
DNA REPLICATION.
Do Now What is replication? Where does this take place?
DNA: The Molecule of Heredity
DNA Replication Making copies.
Deoxyribonucleic Acid
copyright cmassengale
Dna replication SBI4U.
Presentation transcript:

NOTES: CH 16 (part 2) – DNA Replication and Repair

● During DNA replication, base-pairing enables existing (“parental”) DNA strands to serve as templates for new (“daughter”) complementary strands

● Watson and Crick proposed that during DNA replication: 1) the 2 DNA strands separate; 2) each strand is a template for assembling a complementary strand; 3) nucleotides line up singly along the template strand (A-T, G-C); 4) ENZYMES link the nucleotides together at their sugar-phosphate groups.

● Watson and Crick’s proposed model is a SEMICONSERVATIVE model (each of the 2 daughter molecules will have 1 old or CONSERVED strand from the parent molecule and 1 newly created strand)

● DNA replication begins at special sites called ORIGINS OF REPLICATION. -DNA double helix opens at the origin & replication “forks” spread in both directions away from the central initiation site creating a REPLICATION BUBBLE. -100’s to 1000’s of replication origins form in eukaryotic chromosomes, which eventually fuse forming 2 continuous DNA molecules

“Unzipping” the parent DNA strands: ● 2 types of proteins involved with separation of parental DNA strands: *HELICASES: enzymes that catalyze the unwinding of parental DNA double helix to expose template *single-strand binding proteins: keep the separated strands apart & stabilize unwound DNA until new strands can be made

Elongating the new DNA strands: -new nucleotides align themselves along templates of old DNA strands according to base-pairing rules (A-T, G-C)

DNA polymerases catalyze synthesis of new DNA strand: -DNA polymerases link the nucleotides to growing strand. -new strands grow in the 5’ to 3’ direction; new nucleotides are added only to the 3’ end of the growing strand

● Nucleoside triphosphates (nucleotides with 3 phosphate groups linked to the 5’ carbon of the sugar) provides energy for DNA synthesis: -nucleoside triphosphate loses 2 phosphates -exergonic hydrolysis of these phosphate bonds drives the endergonic synthesis of DNA; it provides the energy to form new covalent linkages between nucleotides What is the source of energy that drives the synthesis of the new DNA strands?

Now, back to… DNA polymerase can only add on the 3' end!

*RECALL: DNA strands run in opposite directions; DNA polymerase can elongate strands only in the 5’ to 3’ direction

● this problem is solved by continuous synthesis of 1 strand (LEADING STRAND) and…discontinuous synthesis of the complementary strand (LAGGING STRAND)

● the LAGGING STRAND is produced as a series of short fragments (“Okazaki” fragments) which are synthesized in the 5’ to 3’ direction and then linked together by the enzyme DNA ligase.

● Before new DNA strands can form, there must be small pre-existing PRIMERS to start the addition of new nucleotides -a primer is a short RNA segment that is complementary to a DNA segment -primers are polymerized by primase enzyme

*only 1 primer is necessary for replication of the leading strand, but many primers are necessary to replicate the lagging strand *an RNA primer must initiate the synthesis of each Okazaki fragment! *DNA polymerase removes the RNA primer and replaces it with DNA nucleotides

Hydrogen Bonds Breaking!

Enzymes proofread DNA during its replication and repair damage to existing DNA

 MISMATCH REPAIR: corrects mistakes (mismatched bases) that occur when DNA is being copied *one form of colon cancer is due to a defect in one of the proteins involved in this type of DNA repair

 NUCLEOTIDE EXCISION REPAIR: corrects accidental changes that occur in existing DNA -an enzyme (nuclease) cuts out damaged segment of DNA -the enzymes DNA polymerase and ligase fill in the resulting gaps *xeroderma pigmentosum is caused by an inherited defect in an excision-repair enzyme

What about the 5’ ends of long DNA molecules?  DNA polymerase can only add nucleotides to the 3’ end of a preexisting polynucleotide…  The usual replication machinery provides no way to complete the 5’ ends of daughter DNA strands;  As a result, repeated rounds of replication produce shorter and shorter DNA molecules

Solutions to the problem:  Prokaryotes avoid this problem by having circular DNA molecules…but what about eukaryotes?  The answer is…TELOMERES!

TELOMERES:  special nucleotide sequences at the end of eukaryotic chromosomal DNA molecules;  do not contain genes;  contain multiple repetitions of one short nucleotide sequence  example: in humans, TTAGGG.  # of repeats varies between 100 and 1,000.

TELOMERES:  expendable, noncoding sequences;  they protect an organism’s genes from being eroded through successive rounds of DNA replication.  a special enzyme, TELOMERASE, catalyzes the lengthening of telomeres

Things that make you go hmmmm…  telomerase is NOT present in most cells of multicellular organisms (like ourselves!)…this means  the DNA of dividing somatic cells tends to be shorter in older individuals (older tissues / cells);  thus, telomeres may be a limiting factor in the life span of certain tissues and even the organism as a whole…  telomerase has been found, however, in somatic cells that are cancerous!

A note about chromatin packing…