Ch 14 RNA molecule and RNA processing Flashcards
All of these are modifications of eukaryotic mRNA, EXCEPT
-the formation of a polycistronic molecule.
Polycistronic mRNAs consist of a leader sequence which precedes the first gene. This is not a modification of eukaryotic mRNA.
In eukaryotes, noncoding sequences that interrupt the coding regions are called
introns
In theory, a cell requires _____ different types of tRNA molecules.
20
Because 20 different amino acids are found in proteins, there must be a minimum of 20 different types of tRNA.
What is the key to the functioning of RISCs?
Argonaute
Both siRNA and miRNA molecules combine with proteins to form an RNA-induced silencing complex (RISC). The key to the functioning of RISCs is a protein called Argonaute.
How is it possible to translate more than one type of protein from the same pre-mRNA?
alternative splicing
In alternative processing pathways, a single pre-mRNA can be processed in different ways to produce alternative types of mRNA, resulting in the production of different proteins from the same DNA sequence.
_____ serves as a link between the genetic code in mRNA and the amino acids that make up a protein.
Transfer RNA
Inhibition of gene expression triggered by double-stranded RNA molecules is termed RNA
interference.
Molecules that inhibit gene expression by binding to mRNA sequences and inhibiting their translation are called RNA interference (RNAi).
What is the difference between prokaryotic and eukaryotic ribosomes?
the number of rRNA molecules and proteins
Prokaryotic and eukaryotic ribosomes differ in the number of rRNA molecules and proteins.
_____ are RNAs typically over 200 nucleotides in length and can be as long as 100,000 nucleotides.
lncRNAs
Long noncoding RNAs (lncRNAs) are typically over 200 nucleotides in length and can be as long as 100,000 nucleotides.
Which of these statements is true about gene structure?
The DNA can be much longer than that of mRNA originated from the gene.
The DNA is clearly much longer than the mRNA because regions of DNA looped out from the hybridized molecules.
Which RNA molecules help to cleave and modify eukaryotic rRNAs?
small nucleolar RNAs (snoRNAs)
rRNAs are modified by snoRNAs in the nucleolus where ribosomal subunits are assembled.
_____ are produced from the cleavage of an RNA duplex consisting of two different RNA molecules.
siRNAs
short interfering
Which type of RNA molecule is derived from a long single-stranded RNA transcript and is known to suppress the expression and movement of transposons in the animal germ cells?
PIWI-interacting RNA
(piRNA)
If an mRNA degrades prematurely, in what region might there be a mutation?
3’ untranslated region
The 3’ UTR affects the stability of mRNA and helps regulate the translation of the mRNA protein-coding sequence.
How are rare bases incorporated into tRNAs?
by chemical changes to one of the standard bases
Modified bases arise from chemical changes made to the four standard bases after transcription.
What occurs during the acquisition stage of the CRISPR-Cas system?
Fragments of phage DNA are inserted into the bacterial CRISPR array.
In acquisition, foreign DNA from a bacteriophage or plasmid that enters the cell is identified, processed, and inserted into the CRISPR array.
Which components are NOT found in long noncoding RNA molecules?
exons
Most mRNAs are produced from a single pre-mRNA molecule whose exons are spliced together.
You are running a transcription reaction in your lab. You stop the reaction after a few minutes, and you find that you have three predominant DNA and RNA molecules in your test tube. All have different lengths. The first molecule is 300 nucleotides long, the second is 25 nucleotides long, and the third is 40 nucleotides long. Which molecule is likely the pre-mRNA?
3rd one
