USMLE biochemistry
Terms
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- Chromatin struture
- substance that forms chromosomes. DNA(-) looped around histones."beads of strings"
- Heterochromatin Vs. Euchromatin
-
Hetero-condensed, inactive
Eu- less condensed, active
"truly transcribed" - Nucleotide: Purine
-
A&G (G has KEYtone) with 2 rings,
"PURe As Gold" - Nucleotide: Pyrimidine
-
C,U,T(THYmine has a meTHYL)
"CUT the PY" - Transition vs. Transversion
- TransItion substitute Identical type, transVerion conVersion b/w types
- Mutations in DNA
-
silent-same aa
missense- different aa
nonsense-early stop codon - Prokaryotic DNA replication
-
single origin of replication,
continuous syn. on leading strand, discont. syn. on laging strand (Okazaki fragments). - DNA polymerase III
- elongates chain by adding deoxynulceotides 5' to 3'
- DNA polymerase I
- degrades RNA primer
- Eukaryotic DNA polymerase
- have seperate polymerases for specific functions.
- Eukaryotic genome
- has several origins of replication, AT base pair sequences
- DNA Repair: Single stranded
- glycosylase recognizes and removes damaged base. Endonuclease breaks bases at 5' side. Exonuclease removes nucleotides. DNA polymerase fills gap. DNA ligase seals
- DNA repair defects
-
Xeroderma pigmentosum=UVlight
ataxia-telangiectasia=xrays
Bloom's syndrome= radiation
Fanconi's anemia=cross linking agents - Xeroderma pigmentosum
- defective excision repair, inability to repair thymidine dimers. Sx: dry skin, melanoma
- DNA/RNA/Protein synthesis direction
- 5' to 3'
- mRNA
-
largest, made by RNA polymerase II
"Massive" - rRNA
- most abundant, syn. by RNA polymerase I
- tRNA
- smallest, syn. by RNA polymerase III
- RNA polymerase II
- opens DNA at promotor site. inhibited by alpha amanitin in death cap mushrooms