DNA Replication…Notes Steps: 1. A section of the DNA molecule unwinds and becomes a ___________________ladder. 2. The 2 nucleotide chains are separated by __________________enzymes, which break the hydrogen bonds between the bases. 3. DNA polymerases bind to the 2 sides of DNA moving along in opposite directions, attaching free ___________________to the existing DNA chain. 4. Covalent bonds join sugars and phosphates, __________________bonds join base pairs. • The process of replication happens at many different locations along the DNA ________________________, not just from one end to the other. • Result: 2 new strands of DNA that are exact copies of the original, and the cell is ready to undergo cell division (_______________!). Picture: (see in your book 12-2, pages 333-334) Let’s watch an animation of how this happens! Mutations… • When the bases mis-match themselves in base-pairing, this is one type of ____________. • There is about one error in every 10,000 paired nucleotides but DNA can proof-read itself and repair the mutation, helping keep the error rate to about one error per 1 __________nucleotides. • This has serious effects in new ___________. • Mutations can be bad or good… Good and Bad… • Mutations drive _______________to happen! • Good mutations – help the organism survive longer so that their ___________can be passed down – Examples: camouflage, drug resistant bacteria (good for them, bad for us!) • Bad mutations – cause the organism to __________and not allow those genes to be passed down – Examples: genetic disorders that cause early death, cancer Transcription and Translation Protein Synthesis • What is it? – Transcription happens when DNA is transcribed (making a ________________) into RNA – Translation is when the information is translated into a ________________ Transcription: the process by which genetic information is copied from DNA to _______. Steps: 1. RNA transcription starts on the DNA strand (the template) at the “____________” (initiator or start) gene. 2. RNA polymerase binds to the promoter gene and travels down one side of the ____________________(original DNA) attaching complementary RNA bases and nucleotides. 3. The base pairing rules are the same except U replaces T on the _________strand. 4. This continues until it reaches a DNA region called the “termination signal” (or _________). 5. The RNA polymerase _________________both the DNA molecule and the newly formed RNA molecule (travels to cytoplasm). 6. DNA _______________back up! This newly formed strand is called mRNA or messenger RNA. After mRNA is formed • We are able to make a protein in the cytoplasm. (______________________) • Remember… – The amount and kind of ___________that are produced in a cell determine the structure and function of the cell. – In other words, proteins carry out the genetic __________________________(genes) encoded in our DNA. • mRNA is now grouped into letters of ______ (a group of 3 letters is called a codon). – Each codon will code for one amino acid (AA). – AAs are the __________________blocks of proteins. – A few codons do not code for an AA, instead they signal for translation of an mRNA to ______________(initiator/start codon/promoter) or stop (stop codon/ termination signal). • mRNA is ready to be “_____________” by 2 other types of RNA… rRNA or ________________RNA • When the mRNA gets to the cytoplasm, rRNA (which is in __________________form) will attach itself over the strand. • It helps attach the __________to the mRNA • This is where ribosomes are made! __________ or Transfer RNA • tRNA will locate the start ___________on the mRNA strand and will form the appropriate AA for that codon • tRNA travels down the mRNA to the next codon and forms the appropriate ________ for that codon • The second AA attaches to the 1st & the tRNA molecule ________________from the 1st mRNA codon • This continues until a string/chain of AA are formed = a _________________is made!