Chapter 17 - Gene Expression: From Gene to Protein Flashcards
gene expression
going from gene to protein
the appearance in a phenotype of a characteristic or effect attributed to a particular gene
phenotype
set of observable characteristics of an individual (ex: height, eye color, blood type, etc.)
genotype
the genetic makeup of an organism, the specific combination of alleles for a given gene (ex: Aa, aa, AA, etc.)
genotype => phenotype
what sugar is RNA made of?
ribose
what sugar is DNA made of?
deoxyribose
what are the 4 bases of RNA?
A, U, C, and G
what are the 4 bases of DNA?
A, T, C, and G
what is the shape of RNA?
single-stranded
what is the shape of DNA?
double-stranded, helix shape
transcription
production of RNA from a DNA template
transcribing = 1 nucleotide language to another (DNA to RNA)
what are the 3 parts of transcription? describe them.
(DNA to RNA)
initiation = RNA pol binds to the “promoter”
elongation = RNA pol synthesizes (makes) RNA through base pairing using the DNA template
termination = RNA pol releases RNA
codon
nucleotide triplet (reads RNA in non-overlapping sets of 3)
(ex: AUG MET CCA)
a reading frame is called a codon window
genetic code
the instructions contained in a gene that tells a cell how to make a specific protein
codons are the building blocks of a genetic code
codons = “words”
genetic code = “language”
the genetic code is said to be evolutionarily conserved, what does this mean?
most organisms use the same genetic code to transform their DNA into protein
“the rules governing the correspondence between each codon and its corresponding amino acid or stop signal have remained largely unchanged throughout the course of evolution”
redundant
(relates to the genetic code)
multiple codons per amino acids
unambiguous
(relates to the genetic code)
only one amino acid per codon
translation
RNA-directed (RNA gives instructions) polypeptide synthesis (making)
“translating” nucleotides to amino acid sequences
what are the sites for translation?
ribosomes
what are the 3 types of RNA involved in protein synthesis (protein making)?
messenger RNA = mRNA
transfer RNA = tRNA
ribosomal RNA = rRNA
describe the 3 types of RNA involved in protein synthesis (protein making)
mRNA = carries genetic message in a series of nucleotide triplets (codons)
tRNA = translates nucleotide codons to amino acid sequences
rRNA = catalyzes (causes rxn to occur, activates/speeds up) peptide bond formation between amino acids
what is a peptide bond?
it is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O)
a condensation reaction => forms peptide bond
what type of reaction forms a peptide bond?
dehydration synthesis/condensation reaction
(rxn that causes removal/release of water molecule)
anticodon
nucleotide triplet that pairs w/specific mRNA codons
amino acid attachment site
a location on the ribosome where the amino acid carried by the tRNA is temporarily attached during protein synthesis (protein making)
amino-acyl tRNA synthetase
an enzyme that attaches the appropriate amino acid onto its corresponding tRNA
what is a ribosome?
rRNA-protein complex
(it is made up of ribosomal RNA and proteins)
what are the 3 tRNA binding sites?
A site = tRNA-amino acid
P site = tRNA-polypeptide
E site = empty tRNA exits
(imagine a ribosome sectioned into 3 sections, A | P | E , but it also could look like E | P | A )
true or false: all polypeptides begin with the same amino acids
true
true or false: the translation elongation cycle adds 1 amino acid at a time
true
transformation
“change caused by genes”
change in phenotype (observable traits) due to assimilation of external DNA
true or false: eukaryotic RNA pol requires additional factors for promoter binding
true
transcription
synthesis (making) of a complementary base pairing strands of ribonucleotides
what is the difference between transcription initiation in prokaryotes vs eukaryotes?
prokaryotes = RNA pol recognizes and binds the promoter
eukaryotes = transcription factors bind promoter first, then they help RNA pol get into its position
what is the difference between transcription termination in prokaryotes vs eukaryotes?
prokaryotes = terminator sequence cause RNA pol to be released
eukaryotes = polyadenylation signal recruits proteins that cleave (release) “primary transcript” and release RNA pol
prokaryotes and eukaryotes terminate transcription by distinct mechanisms
untranslated regions (UTRs)
in mRNA
not translated regions that are before the start codon and after the stop codon
5’ UTR = START ===== STOP = 3’ UTR
regulatory functions are the same as the 5’ cap and 3’ tail
what are the functions of the 5’ cap and 3’ poly-A tail?
facilitate export
protect from degradation
facilitate translation
ribosome recruitment
what is the average length of human RNA transcript?
27,000 nucleotides
what is the average length of human protein?
400 amino acids
true or false: eukaryotic mRNA contain non-coding segments interspersed (spread out amongst) w/protein-coding ones
true
true or false: eukaryotic genes are non-continuous
true
exons
protein-coding
contain info to build a protein
introns
non-protein coding
they do not carry info to build a protein
why is it important to remove an intron from the nucleus?
they need to be removed so that mRNA can encode a protein with the right sequence
if the spliceosome fails to remove an intron then an mRNA with extra “junk” in it will be made
the wrong protein will be produced during translation
where are introns located?
inside the nucleus
where are extrons located
outside the nucleus
RNA splicing
it removes introns and then connects the exons
introns - - -
exons = = =
exons introns exons introns exons
=== - - - === - - - ===
to
=== === ===
spliceosome (mr.restocker dude)
RNA-protein complex that carries out splicing
he takes out introns and then connects exons
snRNPs (“snurps”)
small nuclear ribonucleic proteins + snRNA + protein
part of a spliceosome
snRNA
small nuclear RNA
true or false: polypeptide sequences cue ribosomal attachment
true
signal peptide
involved in the process of targeting proteins to the ER
an amino acid sequence that stalls translation and targets ribosomes to the endoplasmic reticulum (ER)
recognized by signal recognition particle (SRP)
escorts to ER-bound receptor
translation resumes
what does a signal peptide do?
the first amino acid sequence that comes out of the ribosome
we see it on some proteins
it is an amino acid sequence in mRNA that stalls translation and targets ribosomes to endoplasmic reticulum (ER)
disappears/is removed once it gets to the ER
signal recognition particle (SRP)
recognizes signal peptides
binds to signal peptide
is a protein-RNA complex
tryptophan
an amino acid that is required for e. coli to survive
trp (italicized) = trp gene
what are the metabolic controls for tryptophan?
1.) enzyme activity = negative feedback and allosteric modulation
2.) enzyme production
negative feedback
a self-regulatory system in which it feeds back to the input a part of a system’s output so as to reverse the direction of change of the output
input to output and then output back into input cycle
the process reduces the output of a system in order to stabilize or re-establish internal equilibrium.
allosteric modulation
a way to control the function of a protein by binding a molecule (allosteric modulator) to a specific site on the protein
there is the protein, the ligand, and the allosteric modulator
the allosteric modulator binds to the protein and changes the shape of the ligand to fit into the active site of the protein
genome
the complete set of DNA (genetic material) in an organism
operon
cluster of function related genes controlled by a single element
what are operons composed of?
promoter = RNA pol binding site
operator = on/off switch which is in or near promoter
controls access of RNA pol to genes
genes = single transcript unit (single mRNA produces various polypeptides)
repressor
a protein that binds operator, blocks attachment of RNA pol
encoded by gene outside the operon
allosterically regulated (can be positively or negatively operated)
what are the two types of operons we need to know?
trp operon and lac operon
lac operon
lac operon = regulates lactose metabolism, codes for the production of enzymes necessary for lactose metabolism
(has an active repressor, which means when an inducer is present it will start making lactase)
trp operon
trp operon = controls biosynthesis of tryptophan (making of tryptophan) in e. coli
(has an inactive repressor which means if the inducer isn’t present the e. coli won’t produce tryptophan)
