Transcription Flashcards
Prashar
what are genes?
units of genetic material
what are the two processes in which proteins are synthesised from genes?
Transcription: genes used as template to synthesise RNA
Translation: RNA used as template to synthesise proteins
what are the 3 essential components in transcription?
- protein coding gene
- RNA polymerase
- Nucleoside triphosphates (NTPs)
what are the 3 phases of transcription?
- initiation
- elongation
- termination
what is the function of a protein coding gene?
important structural features that inform the building of RNA
what is the function of RNA Polymerase?
enzyme that catalyses synthesis of RNA strand from DNA template. also acts as primase by initiating DNA replication
what is the function of NTPs
nucleoside triphosphates are the building blocks of new RNA
what are the three components of a protein coding gene and their functions?
- promoter: specific DNA sequence where transcription begins
- coding sequence: specific DNA sequence, gives coding info for the protein
- terminator: specific DNA sequence that determines the end of the RNA transcript
what polypeptides are present in the core enzyme of RNA polymerase?
2 copies of α, 1 copy of β, 1 copy β’
what poly peptides are present in the halo enzyme of RNA polymerase?
2 copies of α, 1 copy of β, 1 copy β’, 1 copy σ (this subunit dissociates to form core)
what is the function of the halo enzyme?
its sigma σ subunit binds to DNA, specifically the promoter for initiation
what is the function of the core enzyme?
catalysis of transcription
what are the representative NTPs for each of the RNA nucleotide bases?
- uridine triphosphate (UTP): uracil
- cytidine triphosphate (CTP): cytosine
- adenosine triphosphate (ATP): adenine
- guanosine triphosphate (GTP): guanine
where does transcription occur in eukaryotes vs. in prokaryotes?
eukaryotes: in nucleus
prokaryotes: in cytoplasm
what are the three phases of transcription?
A: Initiation
B: Elongation
C: Termination
what happens during initiation and where does it occur?
occurs at promoter: RNA polymerase binds to promoter and begins to unwind the DNA
what happens during elongation?
- rna polymerase moves along DNA template
- rna strand grows by addition of NTPs to its 3’ end in unwound region
- as dna + rna transcript exits rna polymerase, rna is removed from dna template and dna rewinds
what occurs during termination?
- when rna polymerase reaches termination site, rna transcript is released from template
- rna polymerase dissociated from dna, and can perform further rounds of transcription
how are replication and transcription similar?
- phases of initiation, elongation, termination
- involve enzymes that synthesize new complimentary nucleic acid strand
how are replication and transcription different?
- portion of genome transcribed to RNA, whole genome copied during DNA replication
- replication once a cell cycle, transcription all the time
- transcription: copies 1 strand to make 1 mRNA strand, replication copies both strands to make 2 semi conservative DNA strands
- u replaces t as comp base to a
- no primer during RNA synthesis
- RNA polymerase vs DNA polymerase
what is the role and location of activity for small nuclear RNA (snRNA)?
RNA processing, occurs in nucleus
what is the role and location of activity for transfer RNA (tRNA)
translation, adaptor between mRNA and protein sequences, occurs in cytoplasm
what is the role and location of activity for ribosomal RNA (rRNA)?
translation, binding of mRNA and tRNA and protein synthesis, occurs in cytoplasm specifically ribosome
what is the role and location of activity for microRNA (miRNA)?
regulates transcription and translation, occurs in nucleus and cytoplasm
