CH. 13 Transcription Flashcards
where are RNAs synthesized
nucleus
where is mRNA exported to
the cytoplasm- where it is translated
What are the building blocks of RNA
ribonucleotide triphosphates (NTPs)
When does RNA transcription occur
predominantly in G1 and G2 phases
mRNAs are needed for
protein synthesis
any DNA sequence that is transcribed into an RNA molecule
Gene
The coding strand is the
nontemplate strand
Nucleotides are added to the ____ end of the RNA molecule
3’ end
In the tree structure of RNA transcription, 3’ (of DNA) is end with the larger or shorter strands of RNA
shorter
(RNA christmas trees) The 5’ end of the RNA is closer or farther from the DNA
farther
The basal transcription apparatus has
general transcription factors, RNA polymerase
RNA poly II consists of 2 sequences called the…
regulatory and core sequences
core promoter
bound by basal transcription apparatus
is the regulatory promoter upstream or downstream of the core promoter
upstream
transcriptional activator proteins
affect the rate of transcription
consensus sequences
comprise the most commonly encountered nucleotides at each site
What happens in transcription initiation
the transcription apparatus assembles on the promoter and begin the synthesis of RNA
What happens in transcription elongation?
TFIIs left on the promoter and RNA polymerase moves along the DNA template
What happens in termination
Rat1 is a 5’ to 3’ exonuclease that degrades the RNA starting from the 5’ and going to the 3’ until it reaches the transcription machinery once it does this- transcription terminates
What are the different parts of mRNA
5’ methyl cap, 5’ untranslated region, start codon, protein coding region, stop codon, 3’ untraslated region, poly-A-tail
What is the protein-coding region
series of nucleotides specificying the amino acids to the added
what is the function of of mRNA 5’ UTR
necessary for ribosome binding and intron splicing
What is the function of the mRNA 3’ UTR
regulatory role in mRNA stability and translation
why do we need the 5’ methyl cap
needed to start translation, increase stability of mRNA, influences intron splicing, added during transcription by an enzyme coupled by Pol II
What is the first step in pre-mRNA processing
addition of 5’ methyl cap
What is the second step in pre-mRNA processing
Polyadenylation
is the poly-A-tail coded in the DNA
no- it is a post-transcriptional modification
Why is polyadenylation important
increases stability of mRNA, moves mRNA through the cytoplasm, facilitated attachment of the ribosome to the mRNA, is preceded by cleaving of 3’ downstream sequences (pre-mRNAs extend many bases 3’ of the end of the gene)
What is the third step in pre-mRNA processing
intron splicing: stitch together exons and get rid of introns
(in nucleus, done by the spliceosome)
explain the 2 steps of pre-mRNA splicing
The pre-mRNA is cut at the 5’ splice site (frees exon 1 from intron and the 5’ end of the intron attached to the branch point forming a lariat); a cut is made at the 3’ splice site and simultaneously the 3’ end of exon 1 becomes covalently bonded to the 5’ end of exon 2
Alternative Splicing
the same pre-mRNA can be spliced in more than one way to yield different amino acids and therefore different proteins
RNA polymerase I
large rRNAs
RNA poly II
mRNA
RNA poly III
tRNAs
Transcriptional Unit
a stretch of DNA that encodes an RNA molecule and the sequences necessary for its transcription
promoter
initial binding site of RNA polymerase; specifies which polymerase is used for the different classes of genes to be transcribed
Transcription requires 3 major components
a DNA template, raw materials to build a new RNA molecule (NTPS, and the trancription apparatus
The basal transcription apparatus is sufficient to initiate…
minimal levels of transcription
