Chapter 7 Flashcards
what is the central dogma of molecular biology?
flow of genetic info from DNA to RNA to proteins
what is transcription?
copy the nucleotide sequence of DNA into RNA?
what is translation?
use the info in RNA to make protein
how is ribose different from deoxyribose?
RNA has an additional -OH group
what base pair does uracil form with?
adenine
what does transcription produce?
an RNA complement to one strand of DNA
T or F? Does the coding strand of DNA have the same sequence to the RNA product?
true
the RNA chain produced by transcription is called what?
transcript
what enzyme transcribes DNA?
RNA polymerase
what does RNA polymerase do?
catalyzes the formation of the phosphodiester bonds that link the nucleotides together and form sugar-phosphate backbone of RNA
when RNA polymerase moves along the DNA what happens?
unwinding the DNA helix in front of it
what determines where bacterial RNA polymerase starts and stops transcription?
signals in the sequence of a gene
bacterial RNA polymerase contains a subunit called?
the sigma factor
what does the sigma factor recognize?
the promoter on the DNA
once transcription begins, what happens to the sigma factor?
is released and the polymerase continues synthesizing the RNA without it
how long does chain elongation continue?
until the polymerase encounters a termination signal in the DNA
what happens to the polymerase after it is done transcribing?
the poly reassociates with the free sigma factor and searches for another promoter to start process over
what determines the direction of transcription?
the orientation of the promoter at the beginning of each gene
how many types of RNA polymerase are in eukaryotic cells?
3
what does eukaryotic RNA polymerase require to start transcription?
the assistance of a large set of accessory proteins
what are transcription factors?
they assemble at each promoter along with the polymerase before the polymerase begins transcription
RNA polymerase II requires what for transcription initiation?
general transcription factors
how is the TATA box recognized and bounded?
by the general transcription factor TFIID through its subunit called TATA-binding protein (TBP)
The TATA box binding of TFIID then enables the adjacent binding of what?
TFIIB, one of the general transcription factors
what comes together to form a complete transcription initiation complex?
TFIIH and RNA polymerase itself assemble at the promoter to form
what does TFIIH do?
pries apart the double helix of DNA
TFIIH also phosphorylates the long polypeptide tail of RNA poly II by?
releasing it from the general transcription factor so it can begin the elongation phase of transcription
TATA-binding protein (TBP) binds to the TATA box sequence and distorts what?
DNA
TBP is the subunit for what?
the general transcription factor TFIID
what is TFIID responsible for?
for recognizing and binding to the TATA box sequence
what is TBP made of?
a single polypeptide chain. 8 beta sheets sit atop of DNA
phosphorylation of RNA polymerase II allows what?
RNA-processing proteins to assemble on its tail
what are transcribed and processed simultaneously in the nucleus?
eukaryotic RNAs
what type of modifications are made to RNA during processing?
capping at the 5’ end with guanine, polyadenylation at the 3’ ends with poly-A tail, and splicing
why are eukaryotic genes organized differently than bacterial genes?
the coding sequences of most euk genes (exons) are interrupted by noncoding sequences (introns)
what signals the beginning and the end of an intron?
special nucleotide sequences
what are the special sequences recognized by?
by small nuclear ribonucleoprotein particles (snRNPs), which contain small nuclear RNAs (snRNAs) and proteins
what forms the core of the spliceosome, which carries out RNA splicing?
snRNPs
what does spliceosome do?
cleaves the RNA at the intron-exon borders and then covalent link the exons
what does the intron form during splicing?
a branched strucuture
what does a-tropomyosin protein regulates?
the contraction in muscle cells
what is alternative splicing?
allows many different proteins to be produced from same gene
what signals that a mature mRNA is ready for export to the cytoplasm?
RNA-binding proteins
