Chapter 11 Flashcards
Overview of transcription and translation
DNA to RNA to proteins
What is the function of mRNA
It is an intermediate between a gene and a polypeptide
What are transcription enzymes?
RNA polymerases
RNA polymerase moves in what direction?
3’ to 5’
What do RNA polymerases do?
Incorporate nucleotides into an RNA strand, complementary to DNA strand
Where is the proofreading function found?
In transcription
What are operons?
Genes organized in clusters that are transcribed together as single mRNA molecule encoding for multiple proteins
Where does transcription happen in eukaryotes?
In the nucleus
Where do RNA processing steps happen in eukaryotes?
In the nucleus
Where does translation happen in eukaryotes?
In the cytoplasm
Why does translation happen in eukaryotes?
mRNA needs to be exported to cytoplasm
How many types of RNA polymerases are there in eukaryotes?
3
What are the three types of RNA polymerases in eukaryotes?
RNA pol I, II, and III
RNA polymerase I does what?
Transcribed most RNAs
RNA polymerase II does what?
Transcribes mRNAs
RNA polymerase III does what?
Transcribed tRNAs
Which RNA polymerases are only found in plants/
RNA pol IV and V
What doe RNA pol IV and V do?
Transcribes siRNAs
What are the 3 steps of transcription?
1) Initiation
2) Elongation
3) Termination
What do transcription factors binds to?
DNA elements in upstream regulatory regions within upstream promotors and enhancers
What forms the preinitiation complex?
RNA pol II and general transcription factors
Where do general transcription factors assemble?
Pre-initiation complex, upstream of transcriptional start site
What do GTF recruit?
RNA pol II
What is the function of the tail and cap on DNA?
Protect from degradation, help export outside nucleus, and translation process
Where are mRNAs translated?
On ribosomes
What are split genes?
Presence of genes contain intervening sequences
What are exons?
Parts of split gene that contribute to mature mRNAs
What are introns?
Part of split genes that correspond to intervening sequences
What is RNA splicing?
Removal of introns from a pre-RNA
Do transcription factors regulate gene expression?
Yes
A single gene can be controlled by (different, the same) regulatory proteins?
Different
What does the extent to which a gene is transcribed depend on?
Particular combination of transcription factors bound to upstream regulatory elements
What gives rise to phenotypes?
Gene expression
What does RNA processing do?
Trims primary transcripts
How many possible codons are there for 20 amino acids?
64
What codon encodes for methionine?
AUG
What is the starting signal of translation?
AUG
What are the three codons that stop translation?
UAA, UGA, UAG
What can decode the info in an mRNA?
tRNA
What do all mature tRNAs have at their 3’ end?
CCA triplet sequence
Does it require energy to add aas to each tRNA?
Yes
Translation is:
Protein synthesis
What can be seen as the most complex activity of the cell?
Translation
3 steps of initiation of translation?
1) Small subunit/AUG binding
2) Aminoacyl tRNA recruitment
3) Assemble initiation complex
Overall process of translation
1) Initiation
2) Elongation
3) Elongation step 2
4) Elongation step 3
5) Elongation step 4
6) Termination
What plays a major role in selecting tRNAs and ensuring accurate translation?
ribosomal RNAs
What is the first step of elongation?
Aminoacyl-tRNA selection
What is the second step of elongation?
Peptide bond formation between 3 aas
What is the third step of elongation?
Translocation
What is the fourth step of elongation?
Releasing the deacylated tRNA
What is a polyribosome?
A complex of multiple ribosomes on mRNA, allowing simultaneous translation
What do polyribosomes do to the rate of protein synthesis?
Increase rate of protein synthesis
What surveillance mechanism is capable of detecting messages with premature termination?
mRNA surveillance mechanism
