3.4 - Transcription & Protein Processing Flashcards
Purine ribonucleotides
- in RNA
- Have a phosphate, ribose and nitrogenous base
- Adenine & Guanine
Pyrimidine ribonucleotides
- in RNA
- Have a phosphate, ribose and nitrogenous base
- Cytosine & Uracil
RNA
- ribonucleic acid
- ribose instead of deoxyribose
- uracil instead of thymine
- molecules are single-stranded
- are gene length
Transcription
- RNA synthesis using a DNA template
- Has initiation, elongation (of the RNA molecule) and termination
Transcription: Initiation
- RNA polymerase (sigma subunit, specifically) binds to promoter
- includes: RNA polymerase, promoter
- no initiator proteins necessary
- no primer necessary
- no helicases
Consensus sequences for most E. coli promoters
-35 to -10
15-17 bp between the two
Transcription: Elongation
- Addition of RNA nucleotides at 3’ end of growing chain to DNA template strand
- includes: RNA polymerase, NTP precursors
Transcription Component: RNA polymerase
- 5’ -> 3’ polymerase activity
- unwinds DNA template DNA strand
- RNA synthesized 3’ to 5’ direction (as polymerase goes 5’ to 3’)
Transcription: Termination
-Template DNA contains tts (transcription termination signals) that cause termination
2 Types of TTS in E. coli
- intrinsic (requires no other components)
- rho-dependent (requires rho protein)
Molecular Genetics Pathway
DNA > RNA > mature RNA > protein > shape > function > phenotype
mRNA processing in eukaryotes
-From primary transcript RNA created from transcription to a processsed, mature RNA
1) 5’ cap addition
2) 3’ polyadenylation
3) intron removal (exon splicing)
5’ cap addition
- A 7-methylguanosine cap is added to the 5′ end of the pre-mRNA while elongation is still in progress
- 5′ cap protects the nascent mRNA from degradation and assists in ribosome binding during translation
3’ polyadenylation
- poly (A) tail is added to the 3′ end of the pre-mRNA once elongation is complete
- protects the mRNA from degradation, aids in the export of the mature mRNA to the cytoplasm, and is involved in binding proteins involved in initiating translation
Introns and Exons
- Introns: noncoding regions
- Exons: coding rgions
RNA splicing
- Introns are removed and exons joined together
- Spliceosome attach to pre-mRNA by locating 5’ and 3’ splice sites
- Remove the intro sequence alngside SnRNA, that join exons together
- lariat is left-over intron RNA sequence (looks like a loop)
Amino acids (protein structure)
- 20 different amino acids, as 20 different R-groups exist w/ different chemical properties
- has amino group, acidic carboxyl group and R-group
Chemical properties of R-groups
- nonpolar (hydrophobic)
- polar (hydrophilic)
- uncharged
- charged (basic, acidic)
Secondary protein structures
- alpha helix, pleated sheet
- H-bonds between backbone componets
Tertiary protein structures
- B-polypeptide
- can contain a heme (metal group)
- interactions between R-groups in the same polypeptide chain
Quaternary protein structures
- multiple heme groups
- interactions between R-groups of different polypeptide chains
