Exam (elaborations)
USLME - Biochemistry General Questions With Answers @ 2024
- Course
- Institution
USLME - Biochemistry General Questions With Answers @ 2024...
[Show more]
Content preview
USLME - Biochemistry General Questions With Answers @ 2024 Histones are rich in what AAs? - Answer Lysine and arginine (both + charg e) When does histone synthesis occur? - Answer S phase (along with DNA ge tting synthesized) Heterochromatin is _________, euchromatin is _________ - Answer Inactive/conde nsed; active/accessible What allows mismatch repair enzymes to distinguish between old and new DNA strands in prokaryotes? - Answer Methylation; old/template strands ar e methylated, new/daughter strands are unmethylated (and might have error s) Methylated histones are _________ while acetylated histones are __________ - Answe r Inactive "Mute"; active How do you tell thymine and cytosine apart? - Answer THYmine has a m eTHYl group Which is stronger, CG or AT bonds? - Answer CG (three H bonds instead of 2); higher GC content leads to higher melting temp of DNA Amino acids necessary for purine base synthesis - Answer "GAG" = Glycine, Aspa rtate, Glutamine Nucleoside - Answer Base + sugar (nucleoSide = Sugar) Nucleotide - Answer Base + sugar + phosphate (nucleoTide = pho sphaTe) 2 components of a pyrimidine base synthesis - Answer Carbamoyl phosphat e, aspartate Purine synthesis starts with _________ and adds _________ - Answer Sugar/Pi; base Pyrimidine synthesis starts with _________ and adds _________ - Answer Base (orotic acid, later modified); sugar/Pi 2 pathways that involve carbamoyl phosphate - Answer De novo py rimidine synthesis; urea cycle 2 things that can cause orotic aciduria - Answer (1) Ornithine transcaramoylase deficiency (urea cycle), (2) UMP synthase deficiency (pyrimidine synt hesis; this one also has megaloblastic anemia) What is an exception to the genetic code being "commaless" or n onoverlapping? - Answer Some viruses What is an exception to the universality of the genetic code? - Ans wer Human mitochondria Single-stranded binding proteins - Answer Prevent DNA strand from rea nnealing during replication DNA gyrase - Answer Topoisomerase which creates single/double strand br eaks in the DNA to add/remove supercoils; inhibited by fluoroquinolone ABs Primase - Answer Makes an RNA primer on which DNA polymerase III can initiate replication; does this regularly for the lagging strand DNA polymerase III - Answer Prokaryotic polymerase which has 5' -> 3' syn thesis and 3' -> 5' exonuclease activity DNA polymerase I - Answer Prokaryotic polymerase which has 5' -> 3' synthe sis, 5' -> 3' exonuclease, and 3' -> 5' exonuclease activity Telomerase - Answer RNA-dependent DNA polymerase which adds DNA to t he 3' ends of chromosomes to avoid loss of genetic material with every duplic ation; upregulated in cancer cells to increase lifespan Transition mutation - Answer Purine to purine or pyrimidine to pyrimi dine Transversion mutation - Answer Purine to pyrimidine or vice-versa Silent mutation - Answer Codes for same AA (usually changes 3rd po sition of codon "wobble"); protein is same size Missense mutation - Answer Codes for a different AA (e. g. Sickel cell an emia); protein is same size Nonsense mutation - Answer Codes for a stop codon; results in a shor ter, nonfunctional protein Frameshift mutation - Answer Deletion or insertion or 1 or 2 n ucleotides, resulting in misreading of all downstream codons; usually results in shorter, nonfunct ional protein (e. g. DMD) What type of mutation is a conservative mutation? - Answer It is a t ype of missense mutation that codes for a similar AA, so there is no loss of protein foldin g and subsequent function Nucleotide excision repair - Answer Repair process for BIG DNA lesions; endonuc lease removes damaged bases, then DNA polymerase and ligase fill and reseal the gap; associated with xeroderma pigmentosum Enzyme order in nucleotide excision repair - Answer Endonuclease -> DNA polymerase -> ligase Base excision repair - Answer Repair process for SMALL (single base) DNA l esions; glycosylase creates apurinic/apyrimidinic site, endonuclease cleaves 1+ nucleotides from 5' end, lyase cleaves sugar/Pi from 3' end, DNA polymerase-beta fills th e gap, and DNA ligase seals it Enzyme order in base excision repair - Answer Glycosylase, endonuclea se, lyase, DNA polymerase, ligase Mismatch repair - Answer Newly synthesized strand is recognized, mismatched nucleotides are IDed and removed, and polymerase/ligase fill/reseal th e gap; associated with HNPCC Disorder which has defective nonhomologous end joining - Answer Ataxia telangiectasia How does radiation damage DNA? - Answer Double-stranded breaks DNA is synthesized __ to __, while proteins are synthesized __-terminus to __-t erminus - Answer 5'; 3'; N; C DNA is read __ to __; mRNA is read __ to __ - Answer 3'; 5'; 5'; 3' (since we're talking about "reading" the template DNA strand, on which new DNA and mRNA will be ba sed when they are built 5' -> 3') Which end of the DNA has the triphosphate which is the energ y source for the bond? - Answer 5' end Start codon - Answer AUG (codes for methionine in euks and formylm ethionine in proks) 3 stop codons - Answer UGA, UAA, UAG Promoter - Answer Site where RNA polymerase and other TFs bind DNA upstr eam from the gene; AT-rich upstream sequence has TATA and CAAT boxes What happens when you mutate a promoter? - Answer Dramatic de crease in the level of gene transcription Enhancer - Answer Stretch of DNA that alters gene expression by b inding TFs Silencer - Answer Stretch of DNA where negative regulators/represso rs bindThe benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Zayla. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
76669 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now