Exam 12: The Genetic Code and Transcription

What two experimental procedures allowed deciphering of the ordered triplet assignments of the genetic code?

There is some indication that the code is in some way ordered; a certain pattern exists.Describe an observation that supports this view.

Describe the direction of information flow in living systems.Use appropriate,scientific terms in your description.

Which of the following contains the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes?

Sidney Brenner argued that the code was nonoverlapping because he considered that coding restrictions would occur if it were overlapping.A second major argument against an overlapping code involved the effect of a single nucleotide change.In an overlapping code,how many adjacent amino acids would be affected by a point mutation? In a nonoverlapping code,how many amino acid(s)would be affected?

When examining the genetic code,it is apparent that ________.

What is the initiator triplet in both prokaryotes and eukaryotes? Which amino acid does this triplet recruit?

Which of the following two terms relate most closely to split genes?

What is polycistronic mRNA?

An intron is a section of ________.

Of the following three types of nucleic acids-DNA,mRNA,tRNA-which is most likely to contain modified bases?

From the late 1950s to the mid-1960s,numerous experiments using in vitro cell-free systems provided information on the nature of the genetic code.Briefly outline significant experiments in the determination of the genetic code.

Introns are known to contain termination codons (UAA,UGA,or UAG),yet these codons do not interrupt the coding of a particular protein.Why?

Describe how the sigma subunit (factor)of E.coli RNA polymerase participates in transcription.

The relationship between a gene and a messenger RNA is that ________.

When scientists were attempting to determine the structure of the genetic code,Crick and coworkers found that when three base additions or three base deletions occurred in a single gene,the wild-type phenotype was sometimes restored.These data supported the hypothesis that ________.

When considering the initiation of transcription,one often finds consensus sequences located in the region of the DNA where RNA polymerase(s)binds.Which of the following is a common consensus sequence?

A 3' poly-A tail and a 5'-cap are common components of prokaryotic RNAs.

Suppose that in the use of polynucleotide phosphorylase,nucleotides A and C are added in a ratio of 1A:5C.What is the probability that an AAA sequence will occur?

It has been recently determined that the gene for Duchenne muscular dystrophy (DMD)is more than 2000 kb (kilobases)in length; however,the mRNA produced by this gene is only about 14 kb long.What is a likely cause of this discrepancy?