BSI Lecture 5-6 Transcription/Translation Flashcards
Define: transcription
The first step in gene expression when a segment of DNA is copied into mRNA by RNA polymerase.
What is the function of RNA polymerase?
Transcribe genes
Which RNA polymerase produces mRNA?
RNA Polymerase II
Promoter
A DNA sequence to which RNA polymerase binds to begin transcription
What are the three phases of gene transcription?
Initiation, Elongation and Termination
What is the role of the ribosome in translation?
Protein synthesis
What is the function of tRNA in the process of translation?
It carries amino acid to the ribosome
What is the role of the A-site in translation?
The A-site in translation is the entrance for tRNA to be tested for codon/anti-codon match with mRNA.
What is the role of the P-site in translation?
P-site receives amino acid from A-site and adds it to the end of the amino acid side chain.
What is the function of peptidyl transferase?
It forms peptide bond between carboxy terminal of polypeptide chain and amino group of new amino acid. Polypeptide grows from amino to carboxy terminus.
What is the function of elongation factors in the process of translation?
Elongation factors increase accuracy and speed of translational process
What are the stop codons?
UAA, UAG, UGA
Does just one codon code for a specific amino acid?
No, more than one codon can code for a specific amino acid.
What end of the mRNA is considered the beginning, 3’ or 5’?
5’
Define the terms 5’ untranslated region (5’ UTR) and 3’ UTR
5’ UTR is the region of a mRNA that is directly upstream of the initiation codon. 3’ UTR is the region that directly follows the translation termination codon.
Name 5 types of covalent post-translational modifications?
glycosylation, phosphorylation, acetylation, hydroxylation, methylation
Genes contain the instructions to:
Synthesize proteins as well as structural and enzymatic RNA molecules
What types of RNA are genes transcribed into?
mRNA, tRNA, and other RNA molecules.
Which is the only type of RNA that can be translated into a protein?
mRNA
What enzyme transcribe genes?
RNA polymerase I, II, and III
What are the functions of RNA polymerase I?
Transcribes most rRNA genes and produces rRNA.
What are the functions of RNA polymerase II?
Transcribes protein-coding genes and produces pre-mRNA
What are the functions of RNA polymerase III
Transcribes tRNA genes, transcribes some rRNA genes, and produces tRNA and rRNA.
The site where the polymerase starts transcribing the gene forming a pre-mRNA molecule is called the _______
Transcription start site
_______ sequence is the DNA sequence which stops transcription.
Termination
Define “sense” strand
The strand of DNA that is transcribed by the polymerase.
Define “anti-sense” strand
The strand that is not transcribed.
“Upstream” means toward the ______ end of the DNA strand in relations to a particular gene.
3’
T or F; 5’ capping has a guanine nucleotide with a methyl group.
True
Series of repeated adenine nucleotides attached to 3’ end is called ______
Polyadenylation
Capping and polyadenylation of mRNA are important for _____, _______, and ______
Nuclear export of mRNA, mRNA stability, translation of mRNA in cytoplasm
Removal of introns from pre-mRNA is called __________
splicing
________ recognizes a splicing sequence at 5’ and 3’ end of intron.
Spliceosome
T or F; RNA polymerase III excises introns and ligates exons together.
False, spliceosome
Spliceosome structure consists of _____________ and proteins.
small nuclear RNAs (snRNAs)
Where are ribosomes located?
Cytoplasm and Rough ER
Ribosomes subunits: Large (80s) and small (60s). T or F?
False, Large (60s) and small (40s)
Ribosomes are made up of ________ and ______.
Protein; rRNA
Ribosomes are made up of rRNA and 50 ________.
proteins
rRNa and proteins assemble into _____ and _____ subunits.
Large; small
The ______ subunit ribosome contains tRNA binding sites A, P and E.
Large (60s)
Small subunit contains ______ binding site.
mRNA
When an amino acid is attached to the tRNA it is considered “_______” and is called _________
charged; aminoacyl-tRNA
T or F? tRNA is highly folded, 3D structure which is essential for it’s function.
True
____ contains acceptor arm that binds amino acid and an anticodon loop which must recognize codon from mRNA.
tRNA
________ __________ is when tRNMet binds to small ribosome.
Initiation complex
tRNAiMet is the “initiator” tRNA and only used at ______ codon.
start
tRNAmet is used to incorporate Met into the growing polypeptide during __________ phase.
elongation
Initial complex slides along the mRNA until it finds the first start codon which is _____
AUG
_______ sequence is thought to be an important DNA sequence surrounding AUG which helps the initiation complex recognize the first AUG
Kozak
Once the small subunit reaches start codon, eIF’s dissociate to all the large subunit to assemble with tRNAiMet in which site?
P-site
Initiations factor (eIFs) are important because they recognizes 5’ cap and also makes sure mRNA is ________ stranded at the start site.
single
What binds to the poly A tail which acts as a signal that the 3’ end of the mRNA is intact.
Initiations factor (eIFs)
Some initiation factor acts as helicases to relax secondary structure allowing small subunit to scan along the mRNA to find the _____ _____.
start codon
T or F, tRNA with growing polypeptide in P-site is transferred to new amino acid on tRNA that just entered E-site?
False, just entered A-SITE.
Peptidyl transferase forms peptide bond between __________ and __________
carboxy terminal of polypeptide chain ; amino group of new amino acid.
Elongation: Polypeptide grows from ______ to ________ terminus.
Amino; carboxy
Elongation: Ribosome moves forward placing empty tRNA in ___-site and tRNA with growing polypeptide in ___-site, leaving ___-site open for incoming tRNA.
E, P, A
Elongation: Ribosome undergoes ______ _______ to shift the mRNA one codon at a time.
conformational change
Elongation factors (EFs) ______ accuracy and ______ of the translational process.
increase; speed
Termination: Releasing factors are called into play when stop codons ____, ____, or ____ appears in A-site.
UAA, UAG, UGA
Termination: ______ ______ bind to any ribosome with a stop codon in the A-site, which forces ____ _____ enzyme to transfer polypeptide to a molecule of H2O?
Releasing factors; peptydyl transferase
________ is required for many steps in initiation, elongation, and termination.
Energy
In most cells, ______ ______ consumes more energy than any other biosyntheic process.
protein synthesis
What are the two reasons why more than one codon can code for a specific amino acid?
Wobble and tRNA’s with different anticodons can carry same amino acid.
What is wobble?
The ability of one tRNA with a specific anticodon to complementary base pair with more than one codon. Matching the 1st and 2nd codon.
Name the 5 regions of mRNA.
5’ Caps, 5’UTR, Coding sequence (CDS); 3;UTR, 3’ Poly A tail.
What are the 4 post-translational modifications:
Protein Folding; Co-factor binding; Covalent modifications; Assembly with other polypeptides to form quatenary structure
Once the protein is synthesized, most of the time, the first amino acid is _____, which is _____
Cleaved;methionine
The __________ has sequences that functions to regulate stabilization (half-life) of mRNA, length of the poly A tail, rate of which the poly A tail is degraded as well as sequences that regulate the translation of mRNA.
3’ UTR
Introns
DNA sequences that do not contain coding for the amino acid sequence of protein
Exons
contain the coding sequence for the amino acid sequence of the protein
Transcription start site
the site where the polymerase starts transcribing the gene forming a pre-mRNA molecule
Termination sequence
the DNA sequence which stops transcription
Initiation phase
RNA polymerase II binds to promoter
Elongation phase
- moves along DNA from 3’ to 5’
- reads single strand of DNA and adds complementary nucleotides to growing pre-mRNA
- Pre-mRNA synthesized from 5’ to 3’
- contains uracil instead of thymine
Termination phase
RNA polymerase II recognizes termination sequence and releases DNA
Pre-mRNA processing
- 5’ capping - Guanine with methyl group gets added to the 5’ end
- Polyadenylation - series of repeated adenine nucleotides attached to 3’ end (PolyA tail)
- Splicing - introns removed by splicesosomes and ligates exons together
