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Bio Exam 2 content
| Question | Answer |
|---|---|
| What did the work of Gregor Mendel suggest? | That there is a material of heredity and chromosomes during meiosis resembled what Mendel described |
| Purpose of T.H. Morgan's paper about Drosophila..? | It reproduced what Mendel had done, tested a hypothesis about material of heredity |
| What was Morgan's logic in a nutshell? | He studied fruit flies and found that eye color is linked to sex (white eyes appeared mostly in males). He realized this was because the gene for eye color was on the X chromosomes (males only have 1 of these). First solid proof that genes are on chromos |
| What did Nettie Stevens discover? | sex is determined by X and Y chromosomes |
| What was the new concept pertaining to chromosomes and genes? | Genes are on chromosomes |
| What was the Avery Experiment (transforming principle?) | There was rough strain (R) that was non-deadly, and smooth strain (S) that was deadly of bacteria. They found that mixing dead viral bacteria with non-deadly alive bacteria killed the specimen, meaning the non-deadly bact. transformed into functional bact |
| What material of heredity is responsible for the transformation (and what transformed?) | DNA! This is because the non-deadly bacteria picked up genes from deadly bacteria to become functional. |
| How was the Avery Experiment tested and how was DNA confirmed the material of heredity? | The virulent bacteria was heat killed each time, and a different molecule was destroyed each time (lipids, carbs, protein, RNA, and DNA). The only mouse that lived was the one where DNA was destroyed. |
| What was the Hershey-Chase Experiment? | There were bacteria phages that infected the bacteria, binding to it to inject material of heredity to determine whether DNA or proteins were the material of heredity. |
| How did the Hershey-Chase experiment go about? | They labeled DNA with radioactive phosphorus (P-32), and protein with radioactive sulfur (S-35). After the bacteria were infected, they found only the radioactive DNA entered the bacteria |
| What was the major conclusion of the Hershey-Chase Experiment? | DNA is the material of heredity |
| Chargaff's rule #1 | The base composition of DNA varies from one species to another |
| Chargaff's rule #2 | Different tissues of the same individual have the same base composition |
| Chargaff's rule #3 | In a given species, the base doesn't change over time |
| Chargaff's rule #4 (VERY IMPORTANT) | A=T, C=G. A+G = C+T. The total abundance of purines=total abundance of pyrimidines. |
| How to remember purines and pyrimidines? | The shorter the word, the bigger the structure!! (purines = A+G, pyrimidines = C +T) |
| What is X-ray crystallography? | a method used to determine the arrangement of atoms of a crystalline solid in 3D space |
| What did Rosalind Franklin's image suggest about DNA? | The X shape suggests a helix, the 10 lines suggest 10 units/turn and a 34 degree angle/turn. It also described two different forms, which were dependent on water content. Finally, phosphates lie on the outside, sugar and bases inward. |
| Basic skeleton structure of DNA | Sugar-phosphate backbones; sugar is connected to a base. 2 hydrogen bonds when A+T bond, 3 hydrogen bonds when C + G bond |
| More components of DNA (Watson and Crick model) | ends are 3' or 5', single-strands are anti-parallel (2 way street), bases are hydrogen bonded on the inside, each chain runs 5' to 3' |
| How was the double helix model tested? | Dickerson Dodecamer |
| What is the dickerson dodecamer? | The method was to create a molecule of a known sequence and analyze the structure via X-ray crystallography. The results were that there were minor differences in the Watson and Crick model |
| Conclusions from the Dickerson Dodecamer | -3D structures of DNA varies with sequence (allows proteins to bind to specific genes) -differences in twist, roll, propellor twists, displacement, etc -departures from B DNA by sequence |
| What is the basic definition of a polymerase? | enzymes that synthesize in a template dependent manner |
| Components of a polymerase | can make DNA or RNA complimentary to the template strand, template can be DNA or RNA, accuracy can be very high, many can edit, and each can be described as "blank dependent blank polymerase" |
| What is DNA replication? | preexisting "parent" strands become separated, each is the template for biosynthesis of a complementary "daughter" strand |
| What did Arthur Kornberg do when he took a biochemist approach? | He grinded up e. coli, separated the components, and looked for polymerase activity in different components (ex. added template, primer, radio-labelled nucleotides) and he discovered polymerase as a result |
| What is the function of DNA polymerase I? | It works in the 5' to 3' direction (add onto 3' END), it cannot start replication from a single stranded DNA, it required energy (ATP), needs a primer, and the enzyme falls off only after a few bases |
| How does the polymerase choose what base next? | it reads the strand, and places the complementary base next. |
| What are the two ends of polymerase? | There is polymerase function-synthesis of new complimentary DNA strand and the exonuclease-removal of incorrect bases |
| What is PCR (polymerase chain reaction)? | it's performed in very small tubes and it alternates between three different steps |
| Step 1 of PCR | Heat sample of DNA to break hydrogen bonds |
| Step 2 of PCR | cool it down to a temperature that allows hydrogen bonds to form |
| Step 3 of PCR | Primers jump in to bind, defines the piece that will be copied |
| Step 4 of PCR | Add thermostable DNA polymerase to catalyze 5' to 3' DNA synthesis |
| What are some problems in vivo chromosome replication | A LOT here are a few: no single stranded template, DNA needs to be "unzipped" prior to new synthesis, no 3' to 5' polymerase, etc |
| Helicase function | unzips DNA |
| SSBs | temporarily bind to the single stranded DNA, which prevents hydrogen bonds from reforming |
| What is the replication fork? | the spot where DNA is being copied |
| What is the leading strand? | the side of DNA that is copied continuously as DNA unzips. (ex. writing in a straight line without lifting the pen) |
| What is the lagging strand? | the side of DNA that is copied in small pieces because it runs in the opposite direction of how DNA is normally copied (okazaki fragments). they're later joined to make a full strand |
| Gyrase function | alleviates the torsional stress. It's a type of topoisomerase |
| Topoisomerase function | enzyme that alters the structure of DNA |
| What can DNA polymerases NOT do but RNA polymerases CAN do? | they can't begin synthesis, just build onto a preexisting strand. But RNA polymerase can begin synthesis |
| Why does the lagging strand need to be replicated in fragments? | Because polymerases can only synthesize DNA in the 5' to 3' direction, adding nucleotides to the 3' end. |
| Ligase function | utilizes energy from ATP to form the missing bonds between Okazaki fragments, connecting them in a continuous DNA strand. |
| Dimerization domain function | prevents the leading strand polymerase from getting too far ahead of the lagging strand polymerase by binding them together with a dimerization domain. |
| What is the problem/disadvantage of linear chromosomes | with each replication the ends get shorter because the lagging strand can never be fully replicated |
| Why is the lagging strand never fully replicated? | Because DNA needs a primer to begin copying and copying happens in fragments. At the very end of the chromosomes, there's no room for a final primer so the last bit of DNA is left out |
| Telomerase function | enzyme that extends chromosome ends. Without this, telomeres shorten with each cell division |
| How does telomerase work? | It's an RNA dependent DNA polymerase that extends the ends of linear chromosomes by adding a short sequence of nucleotide, maintaining their integrity. |
Created by:
madalynes