Biology 2581B Study Guide - Quiz Guide: Internal Ribosome Entry Site, Eukaryotic Translation, Cis-Regulatory Element

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1 Jun 2020

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Practical use of ires (internal ribosomal entry sites) sequences for expression of polycistronic mrnas in eucaryotes ! An internal ribosome entry site, abbreviated ires, is an rna element that allows for translation initiation in a cap-independent manner, as part of the greater process of protein synthesis. In eukaryotic translation, initiation typically occurs at the 5" end of mrna molecules, since 5" cap recognition is required for the assembly of the initiation complex. The location for ires elements is often in the 5"utr, but can also occur elsewhere in mrnas. (iress are often used by viruses as a means to ensure that viral translation is active when host translation is inhibited) An mrna molecule is said to be monocistronic when it contains the genetic information to translate only a single protein chain (polypeptide). This is the case for most of the eukaryotic mrnas regulated together in a regulatory region, containing a promoter and an operator.

Related Questions

Please please please I reallly need help with the following 5 questions.

Question 1

Which of the following is responsible for directing the prokaryotic ribosome to the +1 start site:

	a.	the 3' UTR
	b.	the AUG codon
	c.	Kozak sequence
	d.	Okasaki fragment
	e.	Shine Dalgarno sequence

Question 2

In translation, mRNAs are READ in the:

	a.	5' to 3' direction and polypeptide chains are synthesized amino to the carboxyl ends
	b.	5' to 3' direction and polypeptide chains are synthesized carboxyl to the amino ends
	c.	3' to 5' direction and polypeptide chains are synthesized carboxyl to the amino ends
	d.	3' to 5' direction and polypeptide chains are synthesized amino to the carboxyl ends

Question 3

Which of the following terms describes a tRNA to which an amino acid has been added:

	a.	charged tRNA
	b.	activated tRNA
	c.	stimulated tRNA
	d.	hydrolyzed tRNA

Question 4

The ability of some tRNA to recognize more than one codon in mRNA is explained by which of the following:

	a.	a reading frameshift
	b.	a reading mistake
	c.	Redundancy Theory
	d.	Wobble Hypothesis

Question 5

One essential component in eukaryotic mRNAs recognized by translation initiation factors is the

	a.	TATA box
	b.	AUG initiation codon
	c.	7-methylguanosine cap
	d.	Shine-Dalgarno sequence

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22. What is probably the single most important distinction between bacteria and eukaryotes?

a. transcription

b. the separation of the cell's genetic material from the surrounding cytoplasm

c. the existence of ribosomes

d. RNA processing in bacteria

e. antibiotics

23. Which one does NOT characterize an open reading frame (ORF)

a. Uses six reading frames during translation

b. Contains a start codon

c. Contains a stop codon

d. Its length is in multiples of 3 nucleotides

e. It should have the number of codons for a protein or on average ~250 codons in length.

24. Nested intronic genes lie within the non-coding intronic region of a larger gene, and occur in the human genome.

a. True

b. False

25. How would you characterize this statement: EF-Tu will hydrolyze GTP only if the codon:anticodon & tRNA:amino acid matchings are correct

a. Transcription; initiation steps

b. Transcription; termination steps

c. Translation: initiation steps

d. Tanslation: elongation steps

e. Spliceosome

26. Regarding the transcription unit architecture of the Escherichia coli genome, which one is FALSE?

a. Each of the 4,661 transcription units comprised an average of 1.1 modular units.

b. 3,010 transcription units (~65%) are monocistronic.

c. 1,652 transcription units (35%) contain more than one ORF (polycistronic)

d. The largest transcription unit is equivalent to 16 ORFs with numerous introns.

e. 398 transcription units (~9%) are nested within each other in opposite transcriptional orientation

27. Regarding RNA interference (RNAi), which one is FALSE?

a. It is a common and conserved mechanism in eukaryotic cells.

b. Originally discovered in bacteria and plant viruses.

c. A form of primitive immunity to protect the genome.

d. Pre microRNA (miRNA) genes have been found in introns.

e. Recent research shows that exogenous plant miRNAs in food can regulate the expression of target genes in mammals.

28. Aminoacyl-tRNA synthetases

a. Recognize the 3âUTR

b. The genes for these enzymes fall into the family of inducible genes

c. The enzymes are imported into the nucleus

d. Covalently attaches an amino acid to the appropriate tRNA. This takes place in the cytoplasm.

e. Forms the peptide bond during protein synthesis

29. What is the process by which complementary RNAs are made from a DNA template?

a. translation

b. transcription

c. protein synthesis

d. transduction

e. transliteration

cyanbee225

Fill in the blank. Elongation during translation does NOT involve ____________.

Question 16 options:

	the translation of codons according to the genetic code
	the formation of bonds catalyzed by the ribosome
	complementary base pairing between RNA molecules
	amino acids being linked together in a polypeptide
	reading the DNA template 3' to 5'

For a given gene, what establishes the reading frame for translation?

Question 17 options:

	the location of the enhancer relative to the gene
	the first three nucleotides at the 5' end of the mRNA
	the first three nucleotides at the 3' end of the mRNA
	the start codon in the mRNA
	the location of the promoter relative to the gene

Which of the following is the LEAST likely direct consequence of a substitution mutation?

Question 18 options:

	changing the length of a protein coded for by a gene
	changing one amino acid in a protein
	creating a stop codon
	eliminating a start codon
	changing the length of the DNA molecule containing a gene

Suppose that the pre-mRNA transcript from a eukaryotic gene is 30,000 nucleotides long, and the gene codes for a sequence of 300 amino acids. What is the best explanation for the relationship between these numbers?

Question 19 options:

	only the first 900 nucleotides of the pre-mRNA transcript are translated
	it takes 100 nucleotides to specify a single amino acid
	300 of the nucleotides in the transcript are important, and the rest are "junk"
	only the last 900 nucleotides of the pre-mRNA transcript are translated
	large portions of pre-mRNA transcripts are cut out during RNA processing

Suppose an individual is born into a population with a novel mutation. Is the new mutation an evolutionary change, and why?

Question 20 options:

	no, because it is not a big enough change to count
	yes, because new mutations are always adaptive
	yes, because the appearance of a new genetic variant is a genetic change in a population
	no, because not enough individuals have the mutation for it to matter
	no, because most mutations are not adaptive

Biology 2581B Study Guide - Quiz Guide: Internal Ribosome Entry Site, Eukaryotic Translation, Cis-Regulatory Element

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