Regulating Gene Expression (College Board AP® Biology): Exam Questions

Researchers investigated the effect of diet on DNA methylation, a type of DNA modification during which methyl groups are added to DNA. They studied a group of genetically identical mice, exposing half of them to a high-fat diet and the other half to a normal diet for 12 weeks. They then measured the methylation levels of a gene associated with obesity in liver cells from both groups. The results are shown in Figure 1.

Which of the following conclusions is best supported by the data?

The lac operon is a group of genes found in in prokaryotes that regulates production of the enzyme β-galactosidase. Scientists studied the effect of glucose and lactose sugar on the lac operon in E. coli bacteria. They set up four experimental conditions:

1. no glucose or lactose

2. glucose only

3. lactose only

4. both glucose and lactose

They measured the levels of β-galactosidase enzyme produced by bacteria under each condition.

Which of the following is the correct null hypothesis for this investigation?

Genes involved in tumor development are typically classified into two main categories: oncogenes and tumor suppressor genes.

Which of the following correctly describes the role of tumor suppressor genes?

The phenotype of a cell or organism is determined by the combination of genes that are expressed and the levels at which they are expressed. Figure 1 below shows an example of a mechanism by which levels of gene expression can be regulated.

Which of the following best describes the mechanism shown?

The regulation of gene expression is essential for ensuring that cells produce the right proteins at the right time, influencing both cellular function and organismal development.

Which of the following correctly describe a type of interaction that regulates gene expression?

Plant cells use transcription factors in a similar way to animal cells. One transcription factor found in plant cells is known as PIF. When activated, PIF binds to a promoter region, triggering transcription of the amylase gene and initiating seed germination. PIF is inhibited a repressor protein called DELLA. The activity of PIF is regulated by the plant hormone gibberellin in the process shown in Figure 3.

Which of the following best explains how the application of gibberellin hormone can facilitate the germination of seeds?

Gene expression can be affected by modification of histone proteins. Histones can be modified by the removal of acetyl groups, a process that is catalysed by a group of enzymes known as histone deacetylases (HDACs). Researchers investigated the role of histone acetylation in gene expression. They treated human fibroblast cells with a histone deacetylase inhibitor (HDACi) and measured the expression levels of various genes over several hours. The results for one gene are shown in Figure 2.

Which of the following conclusions about histone acetylation and gene expression is best supported by the data?

Coordinately regulated genes in prokaryotes are grouped in clusters known as operons. Operons contain several genes that code for proteins that work together to perform a single function. Figure 1 shows the trp operon, a group of genes that control the expression of proteins needed for production of the amino acid tryptophan (trp).

Which of the following best explains why the trp operon is an example of a negative regulatory mechanism for regulating gene expression?

A researcher studied the effect of mutations in the DNA of fruit flies (Drosophila melanogaster). The mutations were in a group of genes called Hox genes, and had the following effects:

• Mutation A = Hox gene downregulation, reducing its activity

• Mutation B = Hox gene upregulation, enhancing its activity

• Mutation C = Hox gene deletion

The researcher recorded the following data:

Which of the following is the most likely claim the researcher could make from these observations?

A team of scientists investigated the effects of small interfering RNA (siRNA) expression of a gene that codes for green fluorescent protein (GFP). They exposed human liver cells that had been genetically modified to express GFP to varying levels of siRNA and measured mRNA levels in treated cells. They then compared these levels to mRNA levels in untreated cells. Their results are shown in Figure 1 below. The error bars in Figure 1 represent standard error.

Which of the following best describes the data shown in Figure 1?