October 21 Flashcards
(31 cards)
Operon
Cluster of genes under the control of a single regulatory signal, can be shut down to save resources
Unit of transcription
Area on a chromosome containing the coding sequence and regulatory sequences that direct and regulate synthesis of that protein
Single RNA molecule
Promotor, RNA-coding sequence, terminator
mRNA
short half-life before being degraded by ribonucleases, rapid turnover allows cell to quickly adapt
Polycistronic mRNA
Codes for a group of cotranscribed genes
Genetic Code
Correspondence between the nucleic acid template and the amino acid sequence of the polypeptide product
Codon
triplet of 3 bases encoding a specific amino acid
Anticodon
Found on tRNA, recognizes codon on mRNA
Wobble
base pairing is more flexible for the third base of a codon
Stop codon
nonsense codon, stops translation
UAA, UAG, UGA
Start codon
AUG
codes for N-formylmethionine
Shine-Dalgarno Sequence
Upstream sequence on mRNA, ensures proper reading frame
Open-reading Frame
Begins with AUG followed by codons and then a stop codon in the same reading frame as the start codon
Archean Chromosomes
- resemble bacteria
- circular
- 500-100s of genes
- Bidirectional replication
How do Archaean’s resemble bacteria?
Chromosomes do not have introns
Single-celled divide by binary fusion
No membrane bound nucleus or organelles
Coupled transcription and translation
Single circular chromosomes
Shine-Dalgarno sequences
How are Archaeans like eukaryotes?
DNA packing
Bidirectional replication
Multiple orgins of replication
Promotors
RNA pol
Archaean Replication and Packaging
Similar to eukaryotes
Histones
Reverse DNA gyrase introduces positive supercoils, which are more stable at high temperatures
Histones
Small positively charged proteins bind to DNA
Cluster of 4 form a tetrasome
Nucleosome
DNA/histone complex
Reverse DNA Gyrase
Topoisomerase that introduces positive supercoils
Gene Expression
Genetic information stored as DNA is transcribed into RNA, the information is translated to yeild specific proteins
Constitutive proteins
Proteins needed in a cell at about the same level all the time
Modes of Regulation
- Activity regulation- activity of a protein can only be regulated after synthesis, fast
- Control the amount of the enzyme produced (slow)
Regulation of Transcription
- DNA binding proteins interact with DNA in a sequence specific manner. Specficity from interactions between aa side chains and specific chemical groups on nitrogenous bases and sugar phosphate backbone
- Binds to major groove
- Protein dimers interact with inverted repeats on DNA each subunit binds to one of the inverted repeats dimer as a whole binds to both strands
Possible Outcomes of DNA Binding Proteins
- Catalyze a specific reaction on DNA, signaling RNA pol to transcribe
- Block (negative regulation)
- Activate (positive regulation)
