Gene Expression

What is gene expression?

• the amount of a protein from a particular gene in a cell

• the total length of a gene in the DNA

• The number of copies of a gene in an organism

• the amount of mRNA produced for a particular gene

In prokaryotes, where is most gene expression controlled?

• At transcription

• At translation

• during mRNA processing

• After translation

Which of the following would decrease the amount of gene expression for a protein in a cell? Select all that apply.

• Increasing the longevity of the mRNA transcript for that protein.
• Increasing the rate at which the protein is broken down.
• Decreasing the number of mRNA transcripts for that protein.
• Increasing the rate at which the gene for the protein is transcribed

Which of the following is true regarding prokaryotic and eukaryotic gene expression?

• In both prokaryotes and eukaryotes, transcription and translation happens almost simultaneously.
• In both types of cells, the production of proteins is mostly regulated at transcription.
• mRNA transcripts last longer in prokaryotic cells than eukaryotic cells.
• Protein synthesis in prokaryotes does not require ribosomes; it does in eukaryotes.

Which of these is not found as part of a bacterial operon?

• Enhancer region
• Promoter
• Operator
• 1 or more genes

The trp operon turns on the genes for the enzymes needed to make tryptophan in bacterial cells when levels of tryptophan are low in the environment. If you were to replace the genes in the trp operon with the gene for green fluorescent protein, what would you expect to see in a bacterial cell with this modification when grown in a culture medium rich in tryptophan?

• The bacterial cells would glow green
• The bacteria would grow normally but not glow.
• The bacteria would not be able to grow in such an environment
• The bacteria would change the GFP into tryptophan.

A colony of E. coli bacteria is grown in a medium containing both glucose and lactose. What would you expect to happen to the lactose over time?

• Lactose levels would decrease slowly as the genes of the lac operon are expressed at low levels.
• Lactose levels would drop quickly as the genes of the lac operon are expressed at high levels.
• Lactose levels would remain constant since the bacteria prefer to use glucose for energy.
• Lactose levels would increase as bacteria use the expression of the lac operon to turn lactose into glucose.

Which of the following would increase the expression of the lac operon in a culture of bacteria growing in a medium with glucose and no lactose? Select all that apply.

• add lactose

• remove the lac promoter

• add lactose, decrease glucose

• increase concentrations of lac repressor proteins

• decrease glucose concentration

A student inserts the green fluorescent protein (GFP) gene into a plasmid with a lac operon. She puts the GFP gene between the operator region and the first lac gene. The plasmid also contains the gene for ampicillin resistance. She grows the bacteria on 4 different types of petri dishes as seen in the table. Which of the plates should she expect to find the highest amount of fluorescence?

• A
• B
• C
• D

Where would you expect to find gene regulating elements (promoters, enhancers, operators) in the genetic code relative to the location of a gene that codes for a protein?

• Downstream of the gene
• Upstream from the gene
• In an intron in the middle of the gene
• As part of the gene’s genetic code