If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then a. the amino acid inactivates the repressor. b. the repressor is active in the absence of the amino acid. c. the amino acid acts as a corepressor. d. the amino acid turns on transcription of the operon.

Muscle cells differ from nerve cells mainly because they a. express different genes. b. contain different genes. c. use different genetic codes. d. have unique ribosomes.

The functioning of enhancers is an example of a. a eukaryotic equivalent of prokaryotic promoter functioning. b. transcriptional control of gene expression. c. the stimulation of translation by initiation factors. d. post-translational control that activates certain proteins.

Cell differentiation always involves a. transcription of the myoD gene. b. the movement of cells. c. the production of tissue-specific proteins. d. the selective loss of certain genes from the genome.

Which of the following is an example of post-transcriptional control of gene expression? a. the addition of methyl groups to cytosine bases of DNA b. the binding of transcription factors to a promoter c. the removal of introns and alternative splicing of exons d. gene amplification contributing to cancer

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? a. irreversible binding of the repressor to the promoter b. reduced transcription of the operon's genes c. buildup of a substrate for the pathway controlled by the operon d. continuous transcription of the operon's genes

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene a. normally leads to formation of head structures. b. normally leads to formation of tail structures. c. is transcribed in the early embryo. d. is a protein present in all head structures.

Which of the following statements about the DNA in one of your brain cells is true? a. Most of the DNA codes for protein. b. The majority of genes are likely to be transcribed. c. It is the same as the DNA in one of your liver cells. d. Each gene lies immediately adjacent to an enhancer.

Within a cell, the amount of protein made using a given mRNA molecule depends partly on a. the degree of DNA methylation. b. the rate at which the mRNA is degraded. c. the number of introns present in the mRNA. d. the types of ribosomes present in the cytoplasm.

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells? a. Proto-oncogenes first arose from viral infections. b. Proto-oncogenes are mutant versions of normal genes. c. Proto-oncogenes are genetic 'junk.' d. Proto-oncogenes normally help regulate cell division.