Lecture 6- Transcription/Translation Flashcards
What are the 4 bases for RNA?
Adeneine - Uracil
Guanine - Cytosine
What type of sugar does RNA have?
What type of group is on the 2’ carbon of RNA?
Ribose
Hydroxyl (OH-)
In what two ways does the hydroxyl group affect RNA?
- Interferes with the double strand (causing RNA to be single stranded)
- Makes RNA less stable than DNA (phosphate backbone is more susceptible to hydrolysis)
What type of bonds make up the sugar backbone of RNA?
Phosphodiester bonds
True or false: because RNA is single stranded, it cannot form complex structures?
FALSE
Hydrogen bonds can help fold single strand RNA into secondary structures
In secondary structure of RNA, what two ribozyme catalytic activity exists?
rRNA (ribosomal RNA)
snRNP (small nuclear ribonucleoproteins)
What are the four main types of RNA?
mRNA- messanger
tRNA- transfer
rRNA- ribosomal
snRNA- small nuclear
What is the role of mRNA?
Forms template for protein synthesis
What is the role of tRNA?
Carries activated amino acids to ribosomes for protein synthesis
What is the role of rRNA?
Structural core of ribosomes
What is the role of snRNA?
Involved in the processing of DNA and RNA within the nucleus
What type of RNA is eventually translated into a protein?
mRNA
What type of RNA matches mRNA code to appropriate amino acids?
tRNA
_____ reads mRNA and translate to proteins
Ribosomes
Ribosomes are made up of ____ and _____.
RNA and Proteins
What is the site of protein synthesis in the cell?
The ribosome
Where is the TATA box located?
In the promoter region upstream from gene (5’ end)
Why is it called a TATA box?
Contains sequences of thymines and adenines
What are the four steps for transcription initiation?
- Transcription factors (nuclear proteins) bind to the TATA box in promoter region
- Transcription factors recruit RNA polymerase
- RNA polymerase binds to DNA sequence and is activated
- Transcription begins
How is RNA polymerase different than DNA polymerase?
RNA polymerase can unwind DNA, but DNA polymerase cannot in DNA replication (helicase must do this)
Does RNA polymerase require a primer?
No
What direction does RNA polymerase read and synthesize?
Reads 3’ to 5’
Synthesizes 5’ to 3’
Opposite ways of DNA polymerase
True or false: RNA polymerase catalyzes phosphodiester bonds
True!
What type of RNA polymerase makes rRNA?
RNA Polymerase 1
What type of RNA polymerase makes mRNA and snRNA?
RNA Polymerase 2
What type of RNA polymerase makes rRNA, tRNA, and snRNA?
RNA Polymerase 3
Where are mRNA, tRNA, and rRNA made?
Endoplasmic reticulum
Ribosome
Nucleus
Cytoplasm
Nucelus
Where do mRNA, tRNA, and rRNA function?
Endoplasmic reticulum
Ribosome
Nucleus
Cytoplasm
Cytoplasm
What are three post-transcriptional modifications?
5’ capping
3’ poly adenylation
Spicing
What are the two main functions of 5’ capping?
- Protects mRNA from 5’ to 3’ exonuclease degradation
- Region where ribosomes can bind
What is the main function of 3’ Poly adenylation?
Protects from 3’ to 5’ exonuclease degradation
What are non-coding regions called?
Introns
What are codes for proteins called?
Exons
What happens in mRNA splicing?
Spliceosome made of snRNPs removes introns and ligates exons together
What happens in alternative splicing?
Because of splicing different combinations of exons, multiple protein possibilities can form from one gene
How/which direction is mRNA read?
mRNA reads 5’ to 3’
Bases are read in triplets (codons)
What is the start codon?
AUG
What are the 3 stop codons?
UAA- u are annoying
UGA- u go away
UAG- u are gone
Since most amino acids have multiple codons, what does this lead to?
Wobble effect
What is the wobble hypothesis?
Since only the first two codons are precisely paired with the anticodon, an exact tRNA match is not required for the third codon, which leads to wobbling
What is a frameshift mutation?
All codons after mutation are different
What is a point mutation?
Single base added, deleted, or changed
What is a missense mutation?
Changed base causes different amino acid
What is a nonsense mutation?
Changed base causes premature stop codon
What is a silent mutation?
Changed base has no effect
What are anti-codons in tRNA?
Complementary bases of codons
EX: the codon AUG has the anti-codon UAC
What happens to the tRNA after the anti-codon binds to the appropriate codon?
tRNA releases its amino acid
What do both the small subunit and large subunit contain?
rRNA and proteins
What are the two main functions that the small subunit carries out?
- Binds and reads mRNA
- Recruits the large ribosomal subunit when it finds AUG
What are the two main functions that the large subunit carries out?
- Acts as a docking site for tRNAs (APE)
- Catalyzes peptide bonds between amino acids released from tRNAs
What are the four main steps for translation initiation?
- Small ribosomal subunit binds mRNA
- tRNA with anticodon UAC binds AUG start codon at P site
- Large subunit is recruited
- New tRNA binds codon at A site
What site does tRNA with anticodon UAC bind AUG start codon?
P site
What site does new tRNA bind codon?
A site
RNA polymerase binds to the transcription factors at the
Promoter region
3’ poly A tail
Spliceosome
Replication fork
Promoter region
A mismatch between the third base of the codon and the anticodon is referred to as
A point mutation
Missense mutation
Wobble pairing
Frameshift mutation
Wobble pairing
Which of the following is not a function of RNA polymerase?
Unwinds DNA
Reads template strand 3’ to 5’
Synthesizes RNA strand 5’ to 3’
Catalyzes peptide bonds
Catalyzes peptide bonds
Abnormalities in which of the following will most directly impair spliceosome function?
snRNA
tRNA
rRNA
None of the above
snRNA
Abnormalities in the RNA polymerase 2 can lead to defective
mRNA
tRNA
rRNA
More than one answer is correct
mRNA
A point mutation that introduces a premature stop codon is classified as a ________ mutation
Silent
Frameshift
Nonsense
Missense
Nonsense
When do ribosomes stop moving along mRNA?
When they encounter a stop codon in the A site
Since there are no tRNAs with anticodons for stop codons _______ ________ bind to stop codon
Releasing factors
What is the charged substrate called to hold tRNA, ATP, and the amino acid?
think enzyme name
Aminoacyl-tRNA synthetase
Where does tRNA drop the amino acid?
At the ribosome
What are three examples of reversible modifcations?
- Phosphorylation
- Ubiquitylation
- Glycosylation
Think PUG
What is an example of an irreversible modification?
Proteolysis