Transcription – Flashcards

Transfer of genetic information from DNA to RNA

1. ribonucleoside triphosphates are monomers 2. Only one strand of DNA is template for RNA 3. No primer required, de novo synthesis 4. RNA is unstable, short-lived compared to DNA 5. Occurs in nucleus

1. Single-stranded 2. complementary to DNA template strand 3. Can be: Messenger RNA (mRNA) Transfer RNA (tRNA) Small nuclear RNA (snRNA) Ribosomal RNA (rRNA) Micro RNA (miRNA) Identical to DNA nontemplate strand 4. Thymidines replaced with uracil

the binding of RNA polymerase to the promoter in DNA; before this, DNA is unwound

A region of DNA to which RNA polymerase binds in order to initiate transcription

proteins required for initiation, prokaryotes have one, eukaryotes have multiple

RNA polymerase traverses the template strand and uses base pairing complementarity with the DNA template to create an RNA copy

during elongation in transcription, this is the direction which the RNA copy is made from the DNA template

catalyzes the synthesis of an RNA complement to DNA Occurs in the 5' to 3' direction Nucleophilic attack by 3'OH on the nucleotidyl phosphorus atom with the elimination of pyrophosphate Unwinds and rewinds DNA No primer required to initiate polymerization

segment of DNA transcribed to produce one RNA molecule One or several genes

Unit of genetic information that controls the synthesis of one protein or structural RNA molecule

down: towards 3' up: towards 5'

Transcript 3' end produced by endonucleolytic cleavage Conserved sequence AAUAAA Cleavage occurs 11-30 nucleotides downstream from conserved seq. RNA polymerase 2 Poly A tail (200) A's -cleavage and polyadenylation coupled -polyadenylation for increase stability

section of genetic sequence that marks the end of gene on DNA for transcription

the exact point on a transcription unit where transcription ends

strand that does not code for RNA strands encode nucleotides that specify amino acids of gene products

codes for the RNA that is translated into protein complementary to sense strand

immature single strand of RNA; synthesized from a DNA template in the cell nucleus by transcription; comprises the bulk of heterogeneous nuclear RNA

The sequence at the 5' end of an mRNA that is not translated into protein. sequence at the 5′ end, preceding the initiation codon (untranslated)

sequence following the termination codon, at the 3′ end (RNA untranslated)

not expressed but help regulate gene expression removed by splicing only in eukaryotes size varies drastically mutations occur rapidly

A region of a gene that is present in the final functional transcript (mRNA) from that gene expressed

or small nuclear ribonucleoproteins, are RNA-protein complexes that combine with unmodified pre-mRNA and various other proteins to form a spliceosome

complex of specialized RNA and protein subunits that removes introns from a transcribed pre-mRNA (hnRNA) segment

specially altered nucleotide on the 5' end of precursor messenger RNA; vital to creating mature messenger RNA, which is then able to undergo translation; ensures stability

a stretch of RNA which only has Adenine bases

messanger RNA - code for protein

A group of three adjacent nucleotides that initiates polypeptide formation, specifically RNA

describing that most amino acids have multiple codons

The linear correspondence between nucleotide triplets in DNA and amino acids in protein

A sequence of three RNA or DNA nucleotides that specifies (codes for) either an amino acid or the termination of translation (general)

adapters between mRNA and amino acids

Containing a basic amino and side chain, building block of protein

cytosine-cytosine-adenine sequence at the 3' end of the tRNA molecule. This sequence is important for the recognition of tRNA by enzymes critical in translation

located at the 3' end of a tRNA molecule

A nucleotide triplet in a tRNA molecule that aligns with a particular codon in mRNA under the influence of the ribosome, so that the amino acid carried by the tRNA is added to a growing protein chain

A complex organelle (composed of proteins plus rRNA) that catalyzes translation of messenger RNA into an amino acid sequence; made up of two subunits

forms basic structure of ribosomes and catalyze protein synthesis

any of the proteins that, in conjunction with rRNA, make up the ribosomal subunits involved in the cellular process of translation

rRNA is transcribed and assembled here

this ribosomal subunit binds to the mRNA

The region of an mRNA molecule that binds the ribosome to initiate translation

-same process as prokaryotes -extension of RNA chain occurs in bubble -polymerase unwinds and rewinds strands -no primer required -short DNA/RNA heteroduplex Pre-mRNA at 5' end 7 MG cap - unusual 5' 5' triphosphate bond

this ribosomal subunit is summoned by the other subunit

three RNA binding sites

The configuration of several ribosomes simultaneously translating the same mRNA

1. mRNA synthesized in nucleus 2. Proteins synthesized in cytoplasm 3. Prokaryotic often multigenic mRNAs 4. Eukaryotic usually monogenic mRNAs 5. Three RNA polymerases 6. Three modifications of mRNA 7-Methyl guanosine cap on 5' end Poly-A tail on 3' end Splicing out introns

1) 5' end 7 methyl-guanosine cap 2) 3' end polyadenylation 3) Introns: non-coding, "intervening" sequences

-primary transcripts in nucleus - hetereogeneous nuclear RNA (hnRNA) -transported to cytoplasm -Transcripts coated with RNA binding protein for protection from RNases -Eukaryotic RNA t1/2 ~5hrs vs 5min prokaryotic

location: nucleolus products: mRNA but not 5s

location: nucleus products: pre-mRNA and miRNA Jobs: -Initiates transcription in Euks -Causes elongation -Termination

location: nucleus products: tRNA, snRNA, 5s mRNA

Bacteria RNA pol requires a single additional protein for transcription initiation(sigma factor), whereas eukaryotic RNA pol require many additional proteins (called general transcription factors). Eukaryotic transcription initiation must deal with packing of DNA into nucleosomes & higher order forms of chromatin structure; these features are absent in bacterial chromosomes

Required for Initiation of transcription by RNA Pol II Proteins--- denoted "TFII-X" (TFII = TF for Pol II) Bind promoter in a specific order Phosphorylation of Pol II "tail" required for escape from preinitiation complex (begins elongation)

the promoter at the beginning of each gene and transcription can occur off either strand of DNA

lead to recruitment site for other proteins that take part in transcription

Occurs when chain is ~ 30 nucleotides in length During active transcription Why?? Recognized by translation machinery Protect 5' end from degradation

splicing of pre-mRNA

process and chemically modify rRNA

modify snoRNA and snRNA

regulate gene expression by blocking translation of select mRNA

turn off gene expression by directing degradation of mRNA and compact chromatin

5' capping 3' polyadenylation Removal of introns

Prokaryotic transcription much simpler Transcription/translation not separated by cellular compartments Usually occur simultaneously (coupled)

Splicing the exons together requires Highly precise removal of each intron Must be precise, one base addition/deletion will make a huge difference Specific signal sequences required for RNA splicing.....

Two steps: Cleavage Ligations Large and complex RNA/protein structure called spliceosome carries out splicing >40 proteins Numerous small RNAs called snRNA (small, nuclear RNAs) Exist in complexes with proteins called snRNP