Lecture 13 (part two of chapter 15) Flashcards
What RNA polymerase transcribes rRNA?
Pol I
Eukaryotes have ____ RNA polymerases
three
What RNA polmerase transcribes mRNA and some snRNA?
pol II
What RNA polymerase transcribes tRNA and some other small RNAs?
pol III
Each RNA polymerase recognizes its own _____
promoter
RNA Pol I promoters are _____ specific
species
RNA Pol II promoters consist of a ____ _______ that can be composed of a number of elements
core promoter
T or F: The TATA box is included in the core promoter
True
Where RNA Pol III promoters found?
within the gene itself
Where is the initiation of transcription at?
Pol II promoters
T or F: RNA pol II requires a series of transcription factors
True
What are elongation complex factors coordinated by structural features called?
carboxyl terminal domain (CTD)
In eukaryotes, the primary transcript must be modified to become ______ mRNA
mature
How is the primary transcript modified to become mature mRNA?
-addition of 5’ cap
-addition of a 3’ poly-A tail
-removal of introns
Why is the addition of a 5’ cap extremely important?
it provides RNA stabiity
What is the process called where GTP is added to 5’ end, with GTP modified by addition of methyl group, called methyl-G cap
addition of a 5’ cap
What is the 3’poly-A tail created by?
poly-A polymerase
Many eukaryotic genes contain sequences that are ____ represented in mRNA
not
What are the non-coding sequences called?
introns
What are the sequences that will be translated called?
exons
Eukaryotic cells deal with introns by cutting and putting back together the _____ ______ to produce _____ mRNA
primary transcript, mature
What is the putting back together the primary transcript to produce mRNA called?
pre-mRNA splicing
What particles recognize the intron-exon boundaries?
small ribonucleoprotein particles
snRNPs cluster with other proteins to form _______
spliceosome
What structure is responsible for removing introns via splicing?
spliceosome
T or F: there is no observed rule governing the number of introns per gene, or the size of introns and exons
True
What theory explains the presence of introns by suggesting exons are functional domains and intron-exon arrangements represent shuffling of those domains over evolutionary timescale?
exon shuffling
What is all the RNAs produced from a genome called?
transciptome
What are all the proteins produced from a genome called?
proteome
T or F: the ratio of genes o transcripts to proteins is 1:1:1
FALSE
What process is of a single primary transcript being spliced into different mRNAs by including different sets of exons being spliced into different mRNAs by including different sets of exons
alternative splicing
What process can account for deviation from balanced ratio?
alternative splicing
What process can greatly increases the number and variety of proteins encoded in the cell nucleus without increasing the size of the genome?
alternative splicing
What is a key macromolecular machine involved in translation that requires interaction with mRNA and tRNA to synthesize proteins
Ribosomes
What adds amino acids to the acceptor stem of tRNA?
aminoacyl-tRNA
What contains three nucleotides complementary to mRNA codons?
anticodon loop
What is the 2d structure of tRNA called?
cloverleaf
At what prime is the acceptor end in tRNA?
3’
each aminoacyl-tRNA synthetase recognizes only ___ amino acid but ____ tRNAs
one, several
What type of RNA has an amino added via a charging reaction using the energy from ATP
charge tRNA
What RNA is an activated intermediate molecule that can undergo peptide bond formation spontaneously
charged tRNA
Acceptor stem is joined to ______ _______
carboxyl terminus
What does it mean when the acceptor stem is joined to carboxyl terminus?
new peptide bonds are formed between amino group and carboxyl group of linked amino acids
T or F: ribosomes do verify amino acid attached to tRNA
False
What two subunits do ribosomes have?
large and small
What tRNA-binding site binds the tRNA carrying the next amino acid
A (aminoacyl) site
What are the three tRNA-binding sites?
A,P,E
What tRNA binding site binds the tRNA attached to the growing peptide chain?
P (peptidyl) site
What tRNA-binding sire binds the tRNA that carried the previous amino acid added?
E (exit) site
What are the two primary functions of ribosomes?
- decode the mRNA
- form peptide bonds
What subunit of the ribosome decodes the mRNA
primarily small subunit
What is the enzymatic component of the ribosome?
peptidyl transferase
What subunit is peptidyl transferase part of?
the large subunit
What does the peptidyl transferase do?
it forms peptide bonds between amino acids
Is the activity of ribosomes mostly thought to be carried out by rRNA or the protein component?
rRNA
What complex is made up of
1. initiator tRNA charged with N-formylmethionine
2.small ribosomal subunit
3. mRNA strand
initiation complex
What sequence of mRNA positions the small subunit correctly
Ribosome binding sequence (RBS)
Once the components in the initiation complex are joined what is added to it?
the large subunit
What site is the initiator tRNA bound to?
The P site
What site is typically left empty?
the A site
How is initiations in eukaryotes different than prokaryotes?
1.the initiating amino acid is methionine
2.more complicated initiation complex
3. Lack of an RBS
What do eukaryotes have instead of an RBS?
small subunit binds to 5’cap of mRNA
What phase adds amino acids?
elongation
the ____ charged tRNA can bind to empty A site
2nd
In order for elongation to add amino acids it requires a what?
an elongation factor
What is the elongation factor called that binds to tRNA and GTP?
EF-Tu
After the 2nd charged tRNA binds to the empty A site what can then form?
the peptide bond
The addition of successive amino acids occurs as a ____
cycle
What is the successive amino acid cycle?
- matching tRNA anitcodon with mRNA codon
- peptide bond formation
- translocation of ribosomes
T or F: in wobble pairing there are more tRNAs than codons
FALSE
What type of pairing allows for less stringent pairing between the 3’ base of the codon and the 5’ base of the anticodon?
wobble pairing
T or F: Wobble pairing allows a lower number of tRNAs to accommodate all codons
True
Elongation continues until the ribosome encounters a ____ codon
stop
Stop codons do not bind to ______
tRNA
What factors recognize stop codons?
release factors
What do release factors do?
they release the polypeptide from the ribosome
Where in Eukaryotes can translation occur?
in the cytoplasm or the rough endoplasmic reticulum (RER)
What sequence is at the beginning of the polypeptide sequence bind to the signal recognition particle in the cytoplasm?
signal sequence
What recognizes the signal sequence and the SRP complex?
RER receptor proteins
What holds ribosome to RER?
docking
______ is the beginning of the protein-trafficking pathway
protein targeting
What is defined as the heritable change in the genetic material?
mutations
A ______ mutation leads to single-nucleotide variation in populations
point
What is the substitution of one base for another called?
base substitution
What are the two categories of base subsitution?
- transition
- transversion
What type of base substitution is where a purine- purine or pyrimidine-pyrimidine is mutated?
transition
What type of base substitution mutation is where a purine-pyrimidine or vice versa is mutated?
transversion
What are the three classes of point mutations?
- silent
- missense
- nonsense
What type of class of a point mutation is when the same amino acid is inserted, essentially no net effect?
silent mutation
What type of class of a point mutation is where it changed the amino acid inserted?
missense mutation
What type of class of point mutation is where it changed to a stop codon?
nonsense
The gain or loss of 1 to 50 bp is called an ______
insertion/ deletion
What characteristics do frameshift mutations have?
- addition or deletion of a base
- much more profound consequences
- they alter the reading frame downstream
mutations are the starting point for ______
evolution
Human mutation rates can now be measured directly via _____ ______ of parents and their childern
whole-genome sequencing