USMLE STEP 1
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32 questions
| 🇬🇧 | 🇬🇧 |
| 1. DNA loops twice around histone octamer 2. Nucleosome is the histone octamer complex with DNA loops | Characteristics of chromatin structure. What is a nucleosome |
| Condensed, transcriptionally inactive. high methylation, low acetylation Ej: Barr bodies (inactive X Chromosome) | Characteristics of Heterochromatin |
| Less condensed, transcriptionally active. --> Euchromatin is Expressed | Euchromatin Characteristics |
| Represses transcription in DNA --> Methylation makes DNA mute In template strand distingue entre old y new | DNA methylation |
| Reversibly represses DNA transcription, but can activate it. --> Mostly makes DNA mute | Histone methylation |
| Base + deoxyribose (Sugar) | Que es un NucleoSide? |
| Base + Deoxyribose + phosphaTe | Que es un NucleoTide? |
| PURE As Gold --> Adenina y Guanina | Cuáles son las PURINAS? |
| CUT the PY --> Citosina, uracilo, timina | Cuáles son las PIRIMIDINAS? |
| Adenina con timina (2 H bonds) y Guanina con citocina (3 H bonds) Crazy Glue | Cómo son las uniones entre las bases nitrogenadas? |
| 1. deaminación 2. deaminación 3. metilación | 1. Cómo se sintetiza guanina de adenosina? 2. Cómo se sintetiza uracilo de citocina? 3. Cómo se sintetiza timina de uracilo? |
| Leflunamide: dihidroorotato deshidrogenasa MTX, TMP, Pyrimethamine: Dihidrofolato reductasa 5-FU: Thymidylate synthase 6-MP: producción de novo de purinas Mycophenolato: inosine monophosphate dehidrogenase Hydoxyurea: ribonucleotide reductase | Qué inhibe Leflunomide, metrotexate, TMP, pyrimethamine, 5-FU, 6-MP, Mycophenolato, hydroxyurea? |
| Necesaria para degradación de adenosina y deoxiadenosina por lo que aumenta dATP --> tóxico para linfocitos --> Causa SCID | Características de deficiencia de adenosina deaminasa y que hace esta encima? |
| 1. Hipoxantina-Guanina Fosforibosil transferasa (HGPRT) 2. Converts hipoxantina to IMP and guanina GMP. Hay exceso de acido urico y producción de purinas de novo. 3. Hyperuricemia, Gout (orange sand in diaper), Pissed off (aggression, self mutilation), Retardation, disTonia 4. X linked | Características de Lesch-Nyhan syndrome. 1. Enzima deficiente 2. Función 3. Características clínicas 4. Genética |
| Specific base pairing is usually only required in the first 2 nucleotide position | Cual es la Wobble Hypothesis? |
| Methionine and tryptophan | Aminoácidos que solo se codifican poor un codon? |
| Glycine, Aspartate, Glutamine--> GAG | Amino acids necessary for purine synthesis: |
| Y shaped region along DNA template | Replication Fork |
| Unwinds DNA template | Helicase |
| Break in the helix to add or remove supercoils. Irinotecan: topoisomerasa I Etoposide: Topoisomerasa II Fluoroquinolones: prokaryotic topoisomerase II and IV | DNA topoisomerases and inhibitors |
| Elongates leading strand | DNA polymerase III |
| Degrades RNA primer and replaces with DNA | DNA polymerase I |
| Joins Okazaki fragments | DNA ligase |
| 1.Purine to purine or pyrimidine to pyrimidine 2. purine to pyrimidine | Mutations in DNA 1.Transition 2.Transversion |
| El cambio de nucleotido codifica para la misma proteína | Silent Mutation |
| Resulting in changed aminoacid. Sickle cell anemia ( glutamic acid --> valine) Nonsense: codifica para un STOP | Missense mutation and example Nonsense |
| Deletion or insertion of a number of nucleotides not divisible by 3. Causes misreading Duchenne, Tay-Sachs | Frameshift mutation and example |
| Mutation at a splice site | Splice site |