Chapter 11: How Do Genes Work?

1.	What change in the nature of the genetic code could be possible if, instead of two sets of base pairs (A:T, G:C), there were three sets of base pairs? [Hint]
2.	Frederick Griffith conducted experiments testing the virulence of two strains of Streptococcus (R-strain and S-strain). His experiment had 4 specific "treatments" to it. Treatment 1, he injected mice with the R-strain and the mice lived. Treatment 2, he injected mice with the S-strain and the mice died. Treatment 3, he injected mice with heat-killed S-strain and the mice lived. Treatment 4, he injected mice with heat-killed S-strain mixed with R-strain and the mice died. Which treatment in his experiment is considered a control treatment? [Hint]
3.	Frederick Griffith conducted experiments testing the virulence of two strains of Streptococcus (R-strain and S-strain). His experiment had four specific "treatments" to it. Treatment 1, he injected mice with the R-strain and the mice lived. Treatment 2, he injected mice with the S-strain and the mice died. Treatment 3, he injected mice with heat-killed S-strain and the mice lived. Treatment 4, he injected mice with heat-killed S-strain mixed with R-strain and the mice died. Which treatment in his experiment is considered the experimental treatment? [Hint]
4.	How many amino acids are represented in the genetic code by just one codon? [Hint]
5.	What is the most common number of codons that specifies a single amino acid? [Hint]
6.	Below is a hypothetical pathway leading to the production of uracil. If this pathway is blocked by genetic mutation at the step controlled by enzyme #3, the organism would require uracil to grow. What other compounds could substitute for uracil to enable the organism to grow? [Hint]
7.	An organism has 30% cytosine in its DNA. What percent of thymine is in its DNA? [Hint]
8.	Scientists of Beadle and Tatum's day simply could not believe that DNA was the genetic material. Why was this hypothesis so hard to accept? [Hint]
9.	Francis Crick made an important contribution to the nature of the genetic code using insertion and deletion mutants of the rII locus of phage T4. What was this contribution? [Hint]
10.	Proteins are made up of 20 different amino acids. How many fewer amino acids would have to be used in order to have the genetic code be made up of two letter "words"? [Hint]
11.	Beadle and Tatum isolated mutant forms of Neurospora crassa that required arginine for growth. What main conclusions did they come to in their study of these mutant Neurospora? [Hint]
12.	Why are mice killed by smooth (S) strains of Streptococcus, but not rough (R) strains? [Hint]
13.	Jerard Hurwitz and J. J. Furth developed an assay for the enzyme RNA polymerase. What property of RNA, compared to its ribonucleotide monomers, did their assay make use of? [Hint]
14.	If a researcher added a polymer of synthetic DNA that contained only adenine (A) residues to a reaction containing RNA polymerase and ribonucleotide monomers, what base would be found in the RNA polymer produced? [Hint]
15.	The discovery of retroviruses and their mechanism of replication required scientists to rethink the "Central Dogma" of molecular biology. What diagram would represent an appropriate adjustment to this Central Dogma diagram? [Hint]
16.	Medicines have been developed to inhibit the spread of retroviral infections (such as AIDS). These drugs target molecular reactions that occur only in cells infected by retroviruses. What enzyme or molecular process could these drugs target? [Hint]
17.	How many different amino acids would be found in a polypeptide made in an in vitro system for synthesizing proteins if a synthetic RNA were provided that had just cytosine (C) and adenine (A) in random order? [Hint]
18.	Francis Crick was careful in suggesting that the genetic code was made up of triplets. He actually said that his results with deletion and insertion mutations in the rII locus of T4 phage was consistent with a codon being made up of either three bases or multiples of three (3n). Why could this be true? [Hint]
19.	Howard Temin and Satoshi Mizutani discovered that the Rous sarcoma retrovirus particle contains the enzyme reverse transcriptase. Why would it be important for the virus to carry its own reverse transcriptase protein? Why wouldn't the virus just make it from its reverse transcriptase gene after it infects the cell? [Hint]
20.	The sequence of a polypeptide is determined by the order of codons that specify the amino acids in the polypeptide. How many different sequences of codons can specify the polypeptide sequence Methionine-Histidine-Alanine-Leucine? [Hint]
21.	Which of the following are the major functional groups found in chromosomes? [Hint]
22.	Which of the following serves as a template for making proteins from DNA? [Hint]
23.	Which of these describes the function of RNA polymerase? [Hint]
24.	Which of the following is an EXCEPTION to the "Central Dogma" of molecular biology? [Hint]
25.	In a skin cell, which of the following changes may lead to skin cancer? [Hint]
26.	Consider the following two mRNA molecules. Original RNA sequence: Acguguaccg acguuguacc The difference between the two molecules would most likely result in which type of change in the resulting protein molecule? [Hint]
27.	If the DNA of this virus was labeled with 32P and the protein of the virus was labeled with 35S, which molecule(s) would be present inside the cells? [Hint]
28.	Which of the following best describes the hypothesis being tested in the experiment illustrated by Figure 11.1 (page 218) in your textbook? [Hint]
29.	Which of the following statements is true for the metabolic pathway shown? [Hint]
30.	What is the maximum number of different enzymes that can be coded for by a single gene? [Hint]
Some questions in this exercise may have more than one correct answer. And answer choices in this exercise are randomized and will appear in a different order each time the page is loaded.