Chapter 7 Concepts Flashcards
What does the central dogma?
Replication (DNA), Transcription (RNA), Translation (Protein); DNA to RNA to Protein
What are the main differences between RNA and DNA?
1) RNA has a hydroxyl at the 2’ position on the Ribose Sugar
2) RNA is single stranded (although can form significant amounts of secondary structures as in transfer RNAs)
3) RNA uses the nucleotide uracil in place of thymine
What determines the nucleotide sequence of an RNA strand?
the template DNA strand
What type of enzyme makes RNA?
RNA polymerase II does mRNA and miRNA
RNA Polymerase I
synthesizes ribosomal RNAs (form the core of the ribosome and catalyze protein synthesis)
RNA Polymerase II
mRNA (code for proteins) and miRNA (microRNAs regulate gene expression); snRNA (small nuclear ribonuclear proteins): snRNP particles for splicing, spliceosome is a large assembly of RNA and protein molecules that carries out RNA splicing in the nucleus)
RNA Polymerase III
tRNA (helps mRNA transcribe into proteins)
What does RNA polymerase II make?
mRNA, miRNA, snRNA
How are the nucleotides in RNA joined together?
phosphodiester bonds
What RNA polymerase makes ribosomal RNA?
RNA polymerase I
What is ribosomal RNA used for?
forms the core of the ribosome and catalyze protein synthesis
Is RNA also polymerized only 5’-to’3’?
Yes just like DNA
Does RNA polymerase require a primer in bacteria or eucaryotes?
Needs a promoter (often a TATA box present in the promoter that is recognized and bound by TBP (TATA-box binding protein) but not a primer.
Where does the energy come from in RNA polymerization by RNA polymerase?
the energy comes from the incoming nucleotide triphosphate (hydroysis of the phosphoanhydride bonds= high energy)
What is the error rate of RNA polymerase?
RNA polymerase error rate is much higher than DNA polymerase, about 1 in 10,000 amino acids; not as necessary for RNA polymerase to be as high fidelity because you are making many mRNA molecules, so if one misincorporated nucleotide, that mRNA will eventually be degraded, so not as big a problem. A misincorporation in the DNA is the genetic material: You are essentially changing the blueprint for all future mRNAs and protein if this occurs in an exon
Do all genes encode just proteins (think RNAs here)?
genes can be encoded for proteins or specific RNAs that can do tasks (ex: snRNA; rRNA; miRNA; also lnRNA (long non-coding RNAs) that perform specific functions)
What is the promoter in a bacteria?
sigma factor: regulatory subunit for bacterial polymerase primarily responsible for recognizing the promoter sequence of DNA; in bacteria have -10 and -35 promoter sequences specifically bound by sigma factors that form part of the RNA polymerase initiation complex
How does the promoter work in a eucaryotic cell?
Eukaryotes requires TAFs (TBP-associated Factors) that bind to the promoter of eucaryotic genes on the chromosomes ; many genes have a TATA box that is a specific DNA sequence that is bound by TBP (TATA binding protein), which then recruits additional TAFS, once the transcription factors are assembled on the promoter then the RNA polymerase can be recruited to the promoter and initiate transcription; does not require a primer
In a bacteria, what is the regulatory molecule that binds the -35 and -10 sequences?
Sigma factor binds -35 and -10 promoter sequences in bacteria
Does sigma factor open the DNA helix or RNA polymerase in bacteria?
Sigma factor opens up the DNA (this is different from helicase in bacteria that works ahead of the replication fork unwinding the DNA)
How does an mRNA terminate in a bacteria?
A hairpin is formed in the RNA and this causes RNA polymerase to dissociate (two tandem repetitive sequences that fold up into a hairpin)
What is an operon?
set of genes (that are functionally related for a specific biochemical purpose, such as the lactose operon and the tryptophan operon that are transcribed into a single mRNA, in bacteria these mRNAs can be translated immediately as the mRNA is NOT capped, spliced and poly Adenylated and because transcription occurs in the cytosol ribosomes can immediately gain access to the mRNA and start translation into protein
What is an operator sequence?
operator is a DNA sequence that is often bound by an inhibitor protein like the Lac inhibitor protein; blocks access of RNA polymerase to the promoter; prevents transcription of the operon and the production of certain enzymes; when the right signal is received (such as the presence of a certain metabolite such as lactose in the Lac operon) the inhibitor comes off the operator DNA sequence and RNA polymerase can bind and initiate transcription
What is a promoter sequence?
-35 TTGACA -10 TATATT +1 A: specific DNA sequence recognized by sigma factor regulatory subunit of RNA polymerase
What is a terminator sequence in bacteria?
Hairpin formed as mentioned above (two repetitive sequences that can form a hairpin by hybridizing to one another) causes RNA polymerase to pop off mRNA
What is a terminator sequence in a eucaryote?
AAUAA sequence (RNA polymerase zooms past then eventually falls off)
In eucaryotes what must assemble at the promoter before RNA polymerase can bind?
Transcription initiation complex composed of TBP-Associated Factors (TAFs), including TBP (TATA binding protein); these TAFS and also enhancer transcription factors that can be located at great distances can initiate transcription by recruiting RNA polymerase II to the promoter–does NOT require a primer
What is a TATA box?
where general transcription factor attaches; short double helical DNA sequence primarily composed of T and A nucleotides (beginning transcription
What is TBP?
TATA binding protein; binds to TATA box sequences and distorts the DNA to help attract other transcription factors
Are bacterial mRNAs transcribed and translated simultaneously?
Yes- DNA lies directly exposed to the cytoplasm that contains ribosomes on which protein synthesis takes place. As mRNA molecules in bacteria are transcribed, ribosomes immediately attach to the free 5’ end of the RNA transcript and protein synthesis starts.
What is the spliceosome?
The largest assembly of RNA and protein molecules that carries out RNA splicing in the cell (snRNPs)
