GEN BIO 2 - CHAP 16.2 AND CHAP 17

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

• One of the daughter cells, but not the other, would have radioactive DNA.

• Neither of the two daughter cells would be radioactive

• All four bases of the DNA would be radioactive.

• DNA in both daughter cells would be radioactive.

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin of replication. Which of the following events would you expect to occur as a result of this mutation?

• No replication fork will be formed.

• Additional proofreading will occur.

• Replication will occur via RNA polymerase alone.

• Replication will require a DNA template from another source.

Which of the following statements correctly describes Archibald Garrod's hypothesis for how "inborn errors of metabolism" such as alkaptonuria occur?

• Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

• Certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.

• Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

• Enzymes are made of DNA, and affected individuals lack DNA polymerase.

A particular triplet of bases in the template strand of DNA is 5′-AGT-3′. What would be the corresponding codon for the mRNA that is transcribed?

• 3′-UCA-5′

• 3′-UGA-5′

• 5′-TCA-3′

• 3′-ACU-5′

Refer to the metabolic pathway illustrated. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on medium supplemented with which of the following nutrient(s)?

• nutrient A only

• either nutrient B or C

• nutrient C only

• nutrients A and C

Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val?

• 5′-TTG-CTA-CAG-TAG-3′

• 5′-AUG-CTG-CAG-TAT-3′

• 3′-AAA-AAT-ATA-ACA-5′

• 3′-AAA-GAA-TAA-CAA-5′

Which of the following statements best describes the significance of the TATA box in the promoters of eukaryotes?

• It is the recognition site for the binding of a specific transcription factor.

• It sets the reading frame of the mRNA during translation.

• It is the recognition site for ribosomal binding during translation.

• It is the recognition site for ribosomal binding during transcription.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5′ cap and poly-A tail. Which of the following processes would you expect her to find to have occurred?

• The mRNA is quickly converted into a ribosomal subunit.

• The cell adds a new poly-A tail to the mRNA.

• The cell adds a new poly-A tail to the mRNA.

• The molecule is digested by enzymes because it is not protected at the 5′ end.

Use this model of a eukaryotic transcript to answer the following question.

 

E = exon and I = intron

 

5′-UTR E1 I1 E2 I2 E3 I3 E4 UTR-3′

Which components of the previous molecule will also be found in mRNA in the cytosol?

• 5′-UTR I1 I2 I3 UTR-3′

• 5′-E1 E2 E3 E4-3′

• 5′-UTR E1 E2 E3 E4 UTR-3′

• 5′-E1 I1 E2 I2 E3 I3 E4-3′

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is ___.

• TTT

• UUA

• UUU

• AAA