DNA Replication PDF

enetics u lar g mo lec a of gm tra l Do Cen 1 2 Energy comes from the nucleoside triphosphates. E is released by the hydrolysis reaction that cleaves 2 phospha...

enetics u lar g mo lec a of gm tra l Do Cen 1 2 Energy comes from the nucleoside triphosphates. E is released by the hydrolysis reaction that cleaves 2 phosphates and the formation of the creation of a phosphodiester bond between the one remaining phosphate and the hydroxyl group on the 3’ carbon p285 fig. 5 3 Replication, Replication is a duplicate of DNA for cell reproduction Transcription and Transcribing DNA using RNA is transcription. Translation This RNA is translated into proteins, translation. 4 Ve 6 mins* 5  prokaryotes eukaryotes Most of our knowledge of DNA replication has come -smaller and circular -long and linear from the study of bacteria. genomes It is mostly the same in -usually only one -1000s of origins eukaryotes but there are replication origin and and many replication some genomic differences. only one replication bubbles (DNA is so bubble long that only parts are copied at a time) -polymerases -polymerases more varied 6 DNA replication 3:30 mins* worksheet 7 DNA replication, transcription and translation: simplified Watch again at the end, after translation 10 mins 8 What is the order of the enzymes used in DNA replication? DNA helicase Unwinds DNA helix polymerase DNA topoisomerase Smooths out the strand for replication. polymerase DNA RNA primase Places RNA primers on template strands polymerase DNA polymerase III Builds new DNA strands from nucleotides Helicase Fills in gaps in the lagging strand between Okazaki DNA ligase DNA polymerase I fragments; also proofreads final strand RNA primase Catalyzes the formation of a phosphodiester bond DNA ligase between 2 DNA strands and the Okazaki fragments Topoisomerase Repairs damage to DNA, including between DNA polymerase II replication events 9 Epigenetics Ted Ed 5 mins* Genome: the complete set of DNA in a cell Epigenome: all the modifications that regulate the activity (expression) of the genes; these turn on or off genes and so, influence the production of proteins in cells. (epi = on top of) Epigenetics, in modern terms, is the study of how genes are expressed without changing the DNA. Cell differentiation in eukaryotes is a form of epigenetics (from stem cells to specific cells). An epigenome may be short-lived or permanent and inheritable. 10 Unlike genetic changes, epigenetic changes are reversible and do not change your DNA sequence, but they can change how your body reads a DNA sequence. (Centers for Disease Control and Prevention, 2022) 11 How Does Epigenetics Work? Loosely packed for transcription. Tightly packed otherwise. 12 Only on cytosine What type of enzyme would add the biochemical group; methyl, acetyl, phosphoryl? Transferase Repairs DNA among other things 13 Cannabis Use Linked to Epigenetic Changes 14 15 Telomere: a repeating sequence of the same 6 nucleotides at the end of a chromosome that protects coding regions from being lost during replication. The RNA primer is removed but is not replaced with DNA nucleotides. But the telomere is a nonsense sequence so no essential coding is lost. Fig. 4 p293 lost 16  Telomeres and aging A normal human cell divides about 50 times Read p295-7 before stopping, Hayflick limit A cell can no longer divide when telomeres are too short, cell senescence = cell aging It accumulates damage that it cannot repair and dies. We do not yet know whether telomere shortening is a direct cause of aging, or just an indicator of getting old. We do know that lifestyle choices such as smoking and UV exposure can speed up the rate of degradation of the telomeres. Healthy telomeres are looped at the end. A change in this structure could cause cell death. 17  Telomere length affects Cancer is nonstop cell division. How does that happen? the longevity of a cell. Cancer cells produce telomerase which is the enzyme that Allowing the telomere to builds telomeres in egg and sperm cells shorten would allow the Why would inhibiting the production of telomeres be a target of cell to die. cancer research? In theory, but then we might create cancer cells Could we use telomerase to make us immortal? 18