Biol211 Chapter 18

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon, then:

• the amino acid inactivates the repressor

• the repressor is active in the presence of the amino acid

• the amino acid acts as a corepressor

• the amino acid turns on transcription of the operon

Muscle cells differ from nerve cells mainly because they:

• express different genes

• contain different genes

• use different genetic codes

• have unique ribosomes

The functioning of enhancers is an example of:

• a eukaryotic equivalent of prokaryotic promoter functioning

• transcriptional control of gene expression

• stimulation of translation by initiation factors

• post-translational control that activates certain proteins

Cell differentiation always involves:

• transcription of the myoD gene

• the movement of cells

• the production of tissue-specific proteins

• the selective loss of certain genes from the genome

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Which of the following is an example of post-transcriptional control of gene expression?

• the addition of methyl groups to cytosine bases of DNA

• the binding of transcription factors to a promoter

• the removal of introns and alternative splicing of exons

• gene amplification contributing to cancer

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

• irreversible binding of the repressor to the promoter

• reduced transcription of the operon’s genes

• buildup of a substrate for the pathway controlled by the operon

• 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:

• normally leads to formation of head structures

• normally leads to formation of tail structures

• is transcribed in the early embryo

• is a protein present in all head structures

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Which of the following statements about the DNA in one of your brain cells is true?

• Most of the DNA codes for protein

• The majority of genes are likely to be transcribed

• It is the same as the DNA in one of your liver cells

• Each gene lies immediately adjacent to an enhancer

Within a cell, the amount of protein made using a given mRNA molecule depends partly on:

• the degree of DNA methylation

• the rate at which the mRNA is degraded

• the number of introns present in the mRNA

• 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?

• Proto-oncogenes first arose from viral infections.

• Proto-oncogenes are mutant versions of normal genes.

• Proto-oncogenes are genetic “junk.”

• Proto-oncogenes normally help regulate cell division.