1 / 20

Lecture 9

Lecture 9. DNA & Replication. ____________ Genomes. Prokaryotic genomes are made of DNA. Prokaryotic chromosomes can be circular or linear. Genome floats freely within cytoplasm Where is DNA found in prokaryotes? ______________ ______________. Transmission electron micrograph of

tamira
Download Presentation

Lecture 9

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 9 DNA & Replication

  2. ____________ Genomes • Prokaryotic genomes are made of DNA. • Prokaryotic chromosomes can be circular or linear. • Genome floats freely within cytoplasm • Where is DNA found in prokaryotes? • ______________ • ______________ . Transmission electron micrograph of E. coli O157:H7 showing flagella. (Courtesy of the CDC)

  3. ____________ Genomes • The genomes of eukaryotic organisms are made of DNA. • Eukaryotic genomes frequently include several to many linear chromosomes sequestered within membrane-bound nucleus (How many do we have?). • Where is DNA found in eukaryotes? • Nuclear DNA • Extranuclear DNA (Where is extranuclear DNA?) Human epithelial cells stained with DAPI (blue, to show the nucleus) and phallotoxin (red, to show F-actin in the cell body) Courtesy of RL Alford, PhD

  4. Nucleotides and Nucleic Acids

  5. Organic Molecules – Nucleic Acids Nucleic acids (both RNA and DNA) are polymers made up of monomers called ______________. Nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) = genetic material of cells. Names derived from type of sugar contained within molecules = ribose Nucleotides Each monomer of nucleic acid is a nucleotide and consists of 3 portions: - a _________ - one or more _____________________ - one of five cyclic ________________________ +adenine, guanine (double-ringed purines) + cytosine, thiamine or uracil (single-ringed pyrimidines) Image: Ashcraft Wiki

  6. Organic Molecules – Nucleic Acids Nucleic Acid Structure Nucleotides linked by covalent bonds between _________ of one nucleotide and _________of next (sugar-phosphate backbone). Nitrogenous bases extending from it like teeth of a comb. Image: www.geneticengineering.org/.../DNA.htm

  7. Nucleic Acids - DNA DNA is a double stranded molecule, analogous to a ladder. The “ladder” = • two deoxyribose-phosphate chains form the “side rails” • base pairs, linked by hydrogen bonds, form the “rungs”. Purine Bases (double ring) Adenine & Guanine Pyrimidine Bases (single ring) Cytosine & Thymine Base Pairs(purine always pairs with pyrimidine) _________ + _________ _________ + _________ Hydrogen bonds form between specific bases of two nucleic acid chains, forming a stable, ________-________ DNA molecule. Hydrogen bonds twist the phosphate-deoxyribose backbones into a helix. Image: www.biologycorner.com/bio1/DNA.html

  8. Image:whyfiles.org/034clone/dna.html

  9. Nucleic Acid Function Replication Transcription Translation

  10. Replication Copying the genetic material is REPLICATION. Replication occurs prior to ________________, because the new, daughter cell will also need a complete copy of cellular DNA. Replication

  11. DNA Replication • __________ a double-stranded DNA molecule. • Each DNA strand holds the same genetic information, so both strands can serve as templates for the reproduction of opposite strand. • The _________ or __________ strand is preserved and the ______ or ___________ strand is assembled from nucleotides • This is called ___________________ replication. Replication

  12. DNA Replication • The resulting double-stranded DNA molecules are identical. • In a cell, DNA replication must happen before cell division. • _________ replicate their DNA throughout the interval between cell divisions. • In ____________, timings are highly regulated. Replication

  13. ______________ DNA Replication: Replication “Bubbles” • Origin of replication (“bubbles”): beginning of replication • Replication fork: ‘Y’-shaped region where new strands of DNA are elongating Replication

  14. _______________ DNA Replication: One Origin • Prokaryotic DNA is arranged in a circular shape, and there is only one replication origin when replication starts. • Despite these differences, the underlying process of replication is the same for both prokaryotic and eukaryotic DNA. Replication

  15. How Do Nucleotides Put Themselves Together Into Nucleic Acids? • An anabolic polymerization process. - Anabolic or Anabolism is….? _____________________________ - Polymerization = taking monomers and putting them together into polymers (large molecules composed of many monomers). • Polymerization requires ___________ (building blocks) and ________. - Triphosphate deoxyribonucleotides provide both. - These building blocks of DNA bring their own energy for polymerization. Replication

  16. DNA Replication:__________ Nature of DNA • Sugar/phosphate backbone runs in opposite directions. • One strand runs 5’ to 3’, while the other runs 3’ to 5’. •DNA polymerase, enzyme that facilitates addition of nucleotides in building the new DNA strand, • Can only adds nucleotides at the free 3’ end Why is this important? Replication

  17. DNA Replication: Leading & Lagging Strand ________ Strand Synthesis toward the replication fork (only the 3’ to 5’ of the master strand). ________ Strand Synthesis away from the replication fork (Okazaki fragments); joined by DNA ligase. Replication

  18. DNA Replication VIDEO: http://207.207.4.198/pub/flash/24/24.html

  19. Reminder…Why is the DNA copied? Replication occurs prior to cell division, because the new, daughter cell will also need a complete copy of cellular DNA. Replication

  20. Replication Mistakes: _________ of Genes • Change in the nucleotide base sequence of a genome; rare. • Almost always deleterious (bad). • Rarely lead to a protein having a novel property that improves ability of organism and its descendents to survive and reproduce.

More Related