Mcat Chapter 2
Terms
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- gene
- series of DNA nucleotides that code for production of a single polypeptide, or mRNA, rRNA or tRNA
- unique sequence DNA
- DNA regions that code for genes
- repetitive sequence DNA
- DNA regions that don't code for gene
- heterochromatin
- area not being transcribed
- euchromatic
- area actively being transcribed
- Central Dogma
- DNA-> RNA -> protein
- nucleotide
-
bond together with phosphdiester bonds between 3rd C of 1 and 5C of the other; 3' attached to OH
5' attached to sugar - adenine 2 thymine
- 2 H bonds
- C 3 G
- 3 honds
- complementary strands
- curl 2 helix, form major and minor grooves
- double helix diametyer
- 2 nanometers
- DNA replication
- 1 x in cell life
- replisome
- 2 replisomes proceed in opposite direction on chromosome to make it bidirectional
- replication units of replicaons
- replicated segments on chromosome
- DNA helicase
- unwinds DNA
- DNA polymerase
- adds deoxynucleotide to primer; read new strand in 3' - 5' ; writes 5'-3'
- RNA primase
- starts/primes strand with 10 ribonucleotide
- each nucelotide added to new string
- requires removal of pyrophosphate group, this energy is released and used to drive replication
- lagging strand
- continuously interrured and restarted with new primer (okazaki fragments)
- DNA ligase
- ties fragments together to form continuous strand
- exonuclease
- subunit of DNA polymerage and proofreads each new strand
- telomeres
- repeated 6 nucleotide units (100 - 100 units long) that protect chromosome from erosion
- RNA vs. DNA
-
DNA: ds, theymine, deoxyribose, replication, nucleus and mitochondrial matrix
RNA: ss, uracil, ribose, transcription also in cytosol (since no nucleus), can move through pores - mRNA
- delivers DNA code for amino acids to cytosol where proteins are manufactured
- rRNA
- combines with protein to form ribosomes (cell complez that directs protein synthesis and catalyzed in the nucleolus)
- tRNA
- collects amino acids in cytosol and transfers them to ribosomes for incorporation into protein
- RNA
- transcription starts at initiation; inititaion factors (proteins) form transcription initiation coplex, promote sequence? ; indication of beginning pt of transcription
- transcription
- requires promotor whereas replication needs primer; promotor tells RNA pol where to start on DNA; primer = short pc of RNA
- Termination
- termination sequence and proteins dissociate RNA pol from DNA in transcription
- Replication
- makes no distinction between genes
- Transcrtiption
- level of gene regulation, proteins called activators and repressor bind to promotor and repress or activate the activity of RNA pol
- Activators and Repressors
- proteins that regulate gene expression; allosterically regulated by cAMP; many proteins can be transcribed from 1 mRNA, so amplifying effect
- primary function of gene regulation in prokaryotes and multicelluar org
- regulate homeostasis inside and outside of the cell
- prokaryotic mRNA
- includes several genes in single transcript (polycistronic)
- eukaryotic mRNA
- monocistronic
- operon
- unit consisting of operator, promotor, and genes of single prokaryotic mRNA
- lac operon
- codes enzymes that allow E. coli to import and metabolize lactose when glucose is not available. low gluc -> hic cAMP to cAMP binds and activates catabolite activator protein -> binds to cap site -> located upstream to lac operon -> promoter is activated -> proteins transcribed -> downstream is lac operator for binind repressor -> repressor inactivated by lactose lac repressor protein will bind to operator unless lactose binds to lac repressor, if no binding -> prevent lac gene transcription, so lactose induces transctiption of lac gene when glucose around
- post transcriptional processing
- all types of RNA go through (in eukaryotes_ for additional regulation
- 1 degress transcript
- initia mRNA nucleotide sequence is processed in 3 ways: MAD
- MAD
-
processing of 1 degree transcript?
add nucleotide, deletion of nucleotide, modification of nitrogenous base