From DNA to protein Flashcards
(32 cards)
The process of gene expression always involves which process(es) described in the central dogma?
transcription
Some genes that are expressed are functional RNA genes. These RNAs don’t undergo translation to protein because they do their job in the cell as an RNA.
At which step of gene expression can cells amplify the number of copies of a protein made from a single gene?
both transcription and translation
Proteins can be made in large quantities by transcribing many mRNAs from the gene, and then each mRNA can be translated into many copies of the protein. In contrast, if just a few mRNAs are made, only a few copies of the protein are made.
Which nucleic acid often base pairs with itself to fold into complex three-dimensional shapes in the cell?
RNA
RNA is often single stranded and complementary regions will base pair with each other to form secondary and tertiary structures.
What is a difference between the mechanisms of DNA polymerase and RNA polymerase?
DNA polymerase needs a base-paired 3′ −OH for a polymerization reaction to occur; RNA polymerase can polymerize two nucleotides without a base-paired 3′ −OH.
DNA polymerase needs a primer to provide a base-paired 3′ −OH to catalyze the polymerization reaction. RNA polymerase does not need a base-paired 3′ −OH, it can join two nucleotides together without a primer.
Why does RNA polymerase make more mistakes than DNA polymerase?
RNA polymerase does not have proofreading activity.
RNA polymerase lacks the ability to proofread its work, so if an incorrectly base-paired nucleotide is added, it cannot excise the nucleotide and add the correct one.
Which characteristic of a replicating RNA polymerase allows multiple transcripts to be made simultaneously from the same region of DNA?
The RNA transcript dissociates from the DNA template immediately once complete.
RNA transcripts dissociate immediately from the DNA template once they are made. This allows many RNA polymerases to form a “caravan” on the gene, producing many transcripts.
Which type of RNA is converted into protein for performing its cellular function?
mRNA
There are many different types of RNA that perform functions as RNA in the cell and are never translated into protein. These include tRNA, rRNA, and miRNA. The only RNAs that code for proteins are mRNAs.
What performs the function of bacterial sigma factor in eukaryotes?
general transcription factors
Sigma factor is an accessory protein to RNA polymerase in bacteria that helps the polymerase bind to the promoter region. In eukaryotes, this function is performed by a set of proteins called the general transcription factors.
The splicing of introns out of an mRNA molecule is catalyzed by
RNA molecules that base pair with the splice sites to promote intron removal.
Splicing is actually an RNA-catalyzed reaction. The RNA molecules in the snRNPs base pair with regions of the RNA that are to be spliced. This base pairing helps promote the rearrangement of bonds to remove the intron.
Export of RNA from the nucleus requires the RNA to have which characteristic(s)?
5′ cap and poly-A tail
To be exported, RNAs must have the features of a processed mRNA. This includes being properly spliced (no introns), having a 5′ cap and a poly-A tail.
The information in an mRNA molecule is converted into protein sequence using
three consecutive bases, with no overlap between triplets.
The genetic code consists of three consecutive bases and is read in a nonoverlapping fashion. That is, the nucleotides for one triplet are not the part of the next triplet.
The reading frame to use for translating an mRNA into functional protein is determined by the
location of an AUG.
The translation of an mRNA in eukaryotes begins when the initiator tRNA encounters the first AUG in an mRNA. The complex containing the initiator tRNA starts scanning the mRNA from the 5′ end to find the AUG.
How do tRNAs become attached to the correct amino acid?
aminoacyl-tRNA synthetases
Enzymes called aminoacyl-tRNA synthetases recognize tRNAs with a specific anticodon as well as the amino acid for that tRNA and catalyze a reaction to join them together. This is called “charging” a tRNA.
The catalytic sites for peptide bond formation during translation is found in which part of the ribosome?
large subunit RNAs
The catalysis of the peptide bonds in the growing polypeptide chain during translation is performed by the rRNA of the large subunit. The ribosome is a ribozyme; proteins play a largely structural role.
What recognizes the stop codons in an mRNA?
release factor
When the ribosome encounters a stop codon, instead of a tRNA binding, a protein called release factor binds and catalyzes the addition of a water molecule to the carboxyl end of the polypeptide and releases it.
What is the benefit of protein synthesis in polyribosomes?
More protein can be produced from a single RNA.
Having more than one ribosome bound to a single mRNA allows many polypeptide chains to be synthesized simultaneously. This allows much more protein to be produced from one mRNA molecule than if each ribosome had to wait for the previous one to finish.
What is the name of the complex that degrades proteins that have reached the end of their lifespan, are damaged, or are misfolded?
proteasome
Large molecular machines called proteasomes act as garbage disposals for degrading proteins that are old or damaged.
The structure of a proteasome is shown below. What group is recognized by region A to indicate that the protein is marked to be eliminated?
ubiquitin
Proteins marked for elimination have a chain of ubiquitin groups added to them. This is recognized by region A and the protein is then threaded into the central cylinder (B) to be degraded by the protease active sites (D).
Protein concentration can be regulated by all of the steps listed EXCEPT
DNA replication.
Protein levels can be tuned by changing the amount of processed mRNA available to ribosomes. Protein levels are not typically regulated by making more copies of the DNA instructions.
What propertie could help RNA be both an information storage unit and a self-replicating molecule?
RNA can act as a template for making copies of itself.
RNA carries information and, through base-pairing rules, can act as a template for self-replication. This, in addition to its ability to catalyze reactions, suggests it may have been a primitive autocatalytic system on early Earth.
Why is RNA thought to predate DNA in evolution?
The sugar in RNA is easier to make with the organic molecules that were present on primitive Earth.
Although the other selections are true, none of them provide evidence for RNA predating DNA in evolution except that the sugar in RNA, ribose, is more easily produced from formaldehyde, which was abundant in the early environment of Earth.
DNA is a better molecule for long-term storage of genetic information than RNA because
the deoxyribose sugar stabilizes DNA chains.
The deoxyribose sugar allows the nucleotide chains to be more stable and grow to longer lengths, making DNA a superior molecule for genetic information storage. In addition, the presence of thymine (rather than uracil) facilitates the detection and repair of damage.
Wat wordt verstaan onder het centrale dogma van de moleculaire celbiologie?
Het doorgeven van genetische informatie in cellen van DNA naar RNA
naar eiwit. (ECB blz. 224) met DNA als gerepliceerde informatiedrager. Daarnaast wat was er eerder de kip of het ei theorie. Hoe maak je zonder enzymen een kopie van het DNA? WRsch was RNA met enzym activiteit de oervorm.
DNA en RNA zijn chemisch gezien verschillend. Noem twee verschillen en een
overeenkomst tussen DNA en RNA.
Verschillen: Base Uracil ipv Thymine; ribose i.p.v deoxyribose; Dubbel strengs vs enkelstrengs molecuul. DNA langer dan RNA. Overeenkomst: Complementaire baseparing: basen kunnen paren in RNA (intramoleculair) en DNA (tussen strengen).
