Flashcards in Chapter 10: From DNA to Protein: Gene Expression Deck (97):
Is the one gene-one protein hypothesis completely accurate?
no it is an oversimplification
Is the one gene-one polypeptide hypothesis complete accurate?
Whiel this is very useful, it is still a little simpler than real life (some genes do not code for polypeptides)
study of nucleic acids and proteins, often focuses on gene expression
True or false: genes are expressed as RNA
True or false: all RNA is translated into proteins
the information in a DNA sequence (a gene) is copied into a complementary RNA sequence
the RNA sequence is used to create the amino acid of a polypeptide
the modified RNA that came from the complimentary DNA strand
Where does mRNA travel in eukaryotic cells?
from the nucleus to the cytoplasm
gets translated into a polypeptide
nucleotide sequence of it determines the sequence of the amino acids
catalyzes peptide bond formation between amino acids to form a polypeptide
protein synthesis factory
multiple proteins and rRNAs
mediates between mRNA and protein
can bind a specific amino acid and recognize a specific sequence in mRNA
figures out which amino acid should be added to the growing polypeptide
What does DNA expression start with?
transcription to RNA
tue formation of a specific RNA sequence from a specific DNA sequence
What factors are required for transcription?
A DNA template for complementary base pairing
the appropriate nucleoside triphosphates (ex ATP) to act as substrates
an RNA polymerase `
catalyze the synthesis of RNA from the DNA template
all have common structure
do not require primer
Are RNA polymerases processive?
a single enzyme-template binding event results in the polymerization of hundreds of RNA nucleotides
what are the three steps in transcription?
needs a promoter
RNA polymerase binds to the promoter
a special DNA sequence to which the RNA polymerase can bind to very tightly
tell RNA polymerase where to start transcription and which of the two strands to transcribe
orients the RNA polymerase
transcription initiation site
part of the promoter
where transcription begins
5' on the non-template strand and 3' on the template strand
Are all promoters identical?
the RNA polymerase unwinds the DNA and reads in the 3' to 5' direction (copying in the 5' to 3')
RNA polymerase uses the ribonucleoside triphosphates as substrates and catalyzes the formation of phosphodiester bonds
True or false: RNA polymerases and crew have more efficient proofreading mechanisms than DNA
false they are less efficient
True or False; RNA errors are more harmful than DNA ones
lots of RNA copies are made/they aren't around for very long, less potential for harm in copying errors
occurs at specific sequences
sequences within a DNA molecule that are expressed as proteins
interrupt the coding region
exons and introns (basically the whole section complementary to the DNA)
just exons, no introns
Nucleic Acid Hybridization
DNA that you want analyzed denatured and hydrogen bonds broken to separate the pairs
probe incubated within the DNA if it has a base sequence complementary to the target DNA, double helix forms
a single-stranded nucleic acid from another source
Do introns scramble the DNA sequence of a gene?
no they interrupt it
removes the introns and splices the exons together
short stretches of DNA that appear with little variation in different genes that acts as borders between introns and exons
small nuclear ribonucleoprotein particles
surround the consensus sequences
has RNA with complementary sequences to the consensus sequences
RNA protein complex
cuts pre-mRNA releases introns and joins the ends of the exons
Are all exons included in every mRNA?
no they aren't
added to the 5' end of the pre-mRNA as it is transcribed
chemically modified GTP
facilitates binding of mRNA to ribosome and protects the mRNA from degradation
poly A tail
added to the 3' end of the pre-mRNA at the end of transcription assists in export of mRNA from the nucleus and is important for stability
True or false: transcription and translation are coupled in prokaryotes
no nucleus and ribosomes bind to mRNA as it is being transcribed
three letter "words"
specify amino acids
How many variations could triplet codons code for?
codes for methionine
termination signals for translation
once the machinery arrives here, translation stops and the polypeptide is released from the copmlex
True or false: The genetic code is redundant
True or false: The genetic code is ambiguous
each only codes for one
Is the genetic code universal?
very few exceptions
occur because of the redundant of the genetic code
change in the amino acid sequence
result in a premature stop codon
result from the insertion or deletion of one or more base pairs within the coding sequence
new triplets are read
What key events must take place to ensure that the protein made is the one specified by mRNA?
a tRNA must chemically read each mRNA codon correctly
the tRNA must deliver the amino acid that corresponds to the mRNA codon
What molecule links the information contained in each mRNA codon with a specific amino acid?
True or false: tRNAs bind to specific amino acids
When is the tRNA charged?
when it is carrying an amino acid
a triplet of bases on the tRNA (t for antiocodon and tRNA)
which is complimentary to the mRNA codon for the particular amino acid that the tRNA has
What bonds hold the codon and anticodon together?
hydrogen of course
Does tRNA interact with ribosomes?
the specificity for the base at the 3' end of the codon is not always observed
doesn't always occur
ex. GCA GCC and GCU all are recognized bt the same tRNA
True or false; each mRNA codon binds to just one tRNA species, carrying a specific amino acid
What family of enzymes is responsible for the charging of tRNA?
Are aminoacyl-tRNA synthetases specific for amino acids?
yup and the tRNA
How does the reaction that aminoacyl-tRNA synthetases catalyze work?
use ATP to form a high energy cone between the amino acid and tRNA
What is recognized the amino acid or the anticodon on the tRNA?
the anticodon on the tRNA
How many subunits does the ribosome consist of?
In eukaryotes, what do the large subunits and small of the ribosome consist of>
rRNA and proteins
they also interact noncovalently
When the ribosome isn't translating DNA, are the subunits together?
What order does a charged tRNA traverse the ribosome sites in?
A P E
amino acid site
charged tRNA anticodon binds to the mRNA codon, living up the correct amino acid
tRNA adds amino acid to the polypeptide chain
exit site where the tRNA resides before being released from the ribosome and heading up to the cytosol to pick up another amino acid
ribsosome has this
ensures that a charged tRNA with the correct anticodon bings to the right codon
hydrogen bonds form when proper binding occurs, the rRNA makes sires that these hydrogen bonds have formed
What three steps occur in translation?
initiation, elongation, and termination
initiation complex binds to mRNA
small subunit moves until it reaches start codon (AUG)
methionine is first in amino acid sequence
at the end of initiation the methionine charged tRNA is in the P site
charged tRNA and small ribosomal subunit (both bound to mRNA)
ribosomal subunits and methionine charged tRNA
chraged tRNA with anticodon complementary to the second mRNA codon enters the A site
large subunit catalyzes two reactions (breaks bond between methionine and tRNA in P site and catalyzes the formation of a peptide bond between methionine and the amino acid on the tRNA in the A site)
first tRNA moves to E site and leaves second tRNA moves to P site
rinse and repeat (in the 5' to 3' direction)
Peptidyl transferase activity
large ribosomal subunit has this because it can break bond between tRNA and amino acid and form peptide bonds between different amino acid)
True or false: polypeptides grow in the amino to carboxyl direction
elongation ends when a stop codon enters the A site
bond between polypeptide chain and tRNA in P site broken
amino acid separate from the ribosome
part of termination (in translation)
allows hydrolysis of the bond between the pole peptide chain and the tRNA in P site
the strand of mRNA with multiples ribosomes and their polypeptide chains
Can several ribosomes simultaneously translate a signal mRNA molecule?
true or false: the site of a polypeptide's function in the cell may be far away from its point of synthesis at the ribosome
True or false: polypeptides are rarely modified by the addition of new chemical groups that contribute to the function of the mature protein
they often are
Where is the default location for a protein?
short stretch of amino acids that indicates where in the cell the polypeptide should go
Where does a signal sequence bind?
to a receptor protein on the surface of an organelle
What happens if a polypeptide has a signal sequence of 5-10 hydrophobic acids at its N terminus ?
it will be directed to the rough endoplasmic reticulum
the cutting of a polypeptide chain
CUT POLYPEPTIDE CHAINS
long polypeptides containing the primary sequences of multiple distinct proteins
these are cut into final products by proteases
addition of carbohydrates to proteins to form glycoproteins