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Describe how the prokaryotic and eukaryotic ribosomes find the start AUG codon within an mRNA. (5 pt.) 2. What is a polycistronic mRNA? Why do the differences you mentioned in 1 above mean that translation from polycistronic mRNAs is limited to prokaryotes (except for the special case I mentioned in class)?

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Sixta Kovacek
Sixta KovacekLv2
28 Sep 2019

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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

1- Eukaryotic viruses often regulate gene expression throughactivities that alter the mRNA 5' cap or its recognition. Give anexample of such an activity and explain how it alters geneexpression.

2- How are T effector and T memory cells different and what aretheir roles in acquired immunity?

3- what are the similarities and differences between acute andsubclinical infections?

4- why does the adaptive immune system not immediately recognizeand clear herpes simplex virus-1 (HSV-1) when it reactivates (i.e.the latent cycle is broken and becomes lytic again)?

5-Do viruses with segmented genomes such as influenza usesequence-dependent or sequence-independent packaging? why?

6- You isolate mRNA from a virus-infected cell and sequence it.You find that there are many mRNAmolecules present and that theyare in different proportions relative to one another. The mostabundant mRNA is encoded at the 3' end of the parent RNA moleculean the least abundant mRNA is encoded at the 5' end. How was themRNA produced?

7- Explain how alternative splisingcan produce two mRNAs thatstart to encode in the "same frame" but end in an "alternativeframe"

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 3’UTR

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

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