BIOC 300B Lecture Notes - Lecture 12: Lac Repressor, Lac Operon, Housekeeping Gene
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QUESTION 10
If you can drink milk as an adult, it means that you have inherited a mutation in the promoter of your lactase gene (the gene that encodes the enzyme you need to break down lactose). Predict the effect of this mutation:
| The mutation changes the number of domains in the enzyme, which makes it work more efficiently | ||
| The mutation changes the amino acid sequence of the lactase protein | ||
| The mutation increases the number of copies of the lactase gene that will be found in your genome | ||
| The mutation changes whether the lactase sequence is found in an intron or exon | ||
| The mutation affects the expression of the lactase gene |
1.2 points
QUESTION 11
A competitive inhibitor is decreasing the activity of an enzyme. Predict the effect of adding more substrate to the reaction.
| The substrate will increase the reaction rate by binding to the allosteric site | ||
| The substrate will increase the reaction rate by competing with the inhibitor for the active site | ||
| The reaction rate will not change unless the inhibitor can be removed | ||
| The enzyme adjusts its shape so that the substrate, but NOT the competitive inhibitor, can bind | ||
| The substrate will bind to the competitive inhibitor and block its ability to bind to the enzyme |
1.2 points
QUESTION 12
What determines where in the genome a transcription regulator will bind?
| Transcription regulators bind to the 5' UTR region of a gene | ||
| Regulators bind via complementary base-pairing to certain DNA molecules | ||
| Covalent bonds form between the transcription regulator and the atoms of the DNA backbone | ||
| Every eukaryotic gene has a different transcription regulator that will bind to the 5' end of the gene | ||
| Transcription regulators bind to specific DNA sequences via multiple weak non-covalent interactions |
1.2 points
QUESTION 13
What is the basic premise of cell theory?
| DNA -> RNA -> protein | ||
| All cells arise from pre-existing cells | ||
| DNA provides the complete instructions to create a cell | ||
| The identity of a cell is determined through gene expression patterns | ||
| All cells contain the same four basic macromolecules |
1.2 points
QUESTION 14
What is the benefit of using BOTH the lac activator and the lac repressor to control gene expression?
| Using both an activator and repressor enables cells to more accurately determine the amount of lactose available in the environment | ||
| Enzymes to digest lactose are only made when energy is low and lactose is available | ||
| The activator can override the inhibition of the lac operon by the repressor | ||
| The repressor can control the enhancer, while the activator can control the promoter | ||
| When neither the lac activator or repressor is present, expression of the lac operon is too high |
1.2 points
QUESTION 15
What is the histone code used for?
| Phosphorylation and acetylation of DNA affect its ability to be compacted | ||
| Changes to the sequence of DNA change whether DNA will wrap around histone proteins | ||
| Covalent modifications of histones affect the ability of the transcription initiation complex to form | ||
| Histones provide the codon sequences needed for translation to occur | ||
| The histone code affects which amino acids will get added to a polypeptide |
13. The arms of a human and the wing of a bat are _________________ structures, composed of the same bones that have been modified for different functions.
| a. | analogous |
| b. | vestigial |
| c. | homologous |
| d. | convergent |
14. Xeroderma pigmentosum is an autosomal recessive genetic disorder. People who are homozygous for the disease-causing allele have skin that is damaged by exposure to ultraviolet radiation; this can lead to skin cancer at an early age. The mutation that causes this disorder is in a gene that functions:
| a. | to repair DNA by excising (removing) nucleotides damaged by UV light. |
| b. | in lysosomes, to break down lipids that otherwise accumulate in the nervous system. |
| c. | to produce the UV blocking pigment melanin in the skin cells |
| d. | in red blood cells to carry oxygen to the skin. |
15. The Amish are a religious sect descended from a small group of colonists who came to the United States over 200 years ago. Their religious beliefs have kept them isolated from society. The Amish have a much higher than average incidence of both polydactyly (extra fingers and toes) and dwarfism in their communities. This is most likely explained by:
| a. | inheritance of acquired characters. |
| b. | the founder effect. |
| c. | disruptive selection. |
| d. | natural selection. |
16. In the structure of DNA that Watson and Crick proposed, the sides of the "ladder" of the DNA molecule are always the same distance apart, making the molecule a constant width. This occurs because when the bases hydrogen bond to form the rungs of the "ladder", a:
| a. | purine always pairs with a pyrimidine. |
| b. | purine always pairs with a purine. |
| c. | pyrimidine always pairs with a pyrmidine. |
| d. | The structure of the double helix is not determined by how the bases pair. |
17. The RNA transcript of DNA that travels to the cytoplasm, carrying the instructions to make a protein, is called:
| a. | rRNA. |
| b. | tRNA. |
| c. | mRNA. |
| d. | RNA polymerase. |
18. When DNA is replicated, the error rate is approximately one error for every 10,000 nucleotides copied. However, that error rate is reduced to only 1 error for every 1 billion nucleotides. The DNA sequence is "corrected" by:
| a. | repeating S phase to see if the error rate is lower the second time around. |
| b. | enzymes that proofread the DNA and repair errors. |
| c. | messenger RNA during the process of transcription. |
| d. | Any errors made during DNA replication cannot be corrected. If errors are detected after S phase, the cell is destroyed. |
19. Mendel's principle of segregation says that:
| a. | when gametes are formed, each gamete receives only one allele for a particular gene. |
| b. | some genes are dominant to others. |
| c. | a testcross must be used to determine the genotype of an organism with a dominant phenotype. |
| d. | all of the above |
20. Tay-Sachs disease is lethal before reproductive age, but the allele persists in Louisiana French Canadians because:
| a. | it is a dominant allele. |
| b. | new mutations causing this disease are common in that population. |
| c. | it is not expressed in the phenotype of heterozygous individuals. |
| d. | the disease is contagious and can be transmitted by nonheritable means. |
21. Physical features that are similar in organisms which are not closely related to each other are most likely a result of ____________. A good example of this is the similarities seen between some marsupial and placental mammals.
| a. | natural selection. |
| b. | adaptation to similar environments |
| c. | convergent evolution |
| d. | All of the above phrases can be used to correctly fill this blank. |
22. In humans, which of the following sex chromosome compliments could be found in males?
| a. | XY |
| b. | XX |
| c. | Y |
23. The proteins that are associated with eukaryotic chromosomes:
| a. | help to package the DNA within the nucleus. |
| b. | are involved in gene expression, through binding with the DNA. |
| c. | may be replicating or transcribing the DNA. |
| d. | All of these are true of proteins that are associated with eukaryotic chromosomes. |
24. A sequence of DNA nucleotides that contains the information to produce a single protein is a(n):
| a. | codon. |
| b. | gene. |
| c. | polypeptide. |
| d. | anticodon. |
