Exam 11: How Genes Are Controlled

E. coli can synthesize the amino acid threonine or absorb it from the environment. In the thr operon, the repressor is active when it is bound to threonine. If an E. coli bacterium is in an environment where threonine is absent, will transcription of threonine synthesis genes take place? Why or why not?

There is a mutation in the operator of the lac operon in a cell such that the lac repressor always stays bound to the operator. If lactose is added to the cell, what will happen?

What is the proper order of events in the expression of a eukaryotic protein?

Signal transduction pathways

In terms of gene regulation, what do eukaryotes and prokaryotes have in common?

A single cell, the zygote, can develop into an entirely new organism with many different specialized cells. Which of the following statements about this process is false?

The figure below shows a normal cell transduction pathway. If the receptor wasn't there, which of the following is the most likely outcome?

The relationship between DNA and chromosomes is most like

The tortoiseshell pattern on a cat

A homeotic gene

In plants, most differentiated cells retain

Which of the following statements about microarrays is false?

Which of the following processes occurs when a salamander regenerates a lost limb?

A cell has a mutation in both alleles of its p53 gene that causes the p53 protein to be three times as effective as normal. What do you predict would happen to this cell?

Adult stem cells have limited therapeutic potential

What is the correct order of structures in a chromosome from smallest to largest?

Which of the following permits a single gene to code for more than one polypeptide?

After reading the paragraph below, answer the questions that follow. All apples in the United States, regardless of variety or where they're purchased, are produced by cloning. For more than 2,000 years, apple growers around the world have used a type of cloning called grafting to produce larger, better-tasting apples. Why has cloning become the primary method of apple growing? Apples grown from seeds usually don't produce apples with the same taste and appearance as that of the parent tree because there's a high degree of genetic variability among the seeds. Making identical genetic copies of the preferred fruit is the only way to get reliable apple quality. In grafting, the shoots and branches of the desired fruit, called a scion, are attached onto the trunk and root system of a previously existing tree, called the rootstock. Both components of the graft are needed because the rootstock controls gene expression in the scion, triggering production of apples that match the cloned scion. Grafting research can be used to produce some interesting tree combinations that are beneficial for intensive agriculture. For example, if you graft the root of a small tree variety, such as the crab apple, onto the shoot from a larger apple tree, such as the Gala, you can produce Gala apples on a much smaller tree. Other scientists are trying to create disease-resistant varieties that would need fewer pesticides. This is beneficial for the environment and also lowers the price of apples in the grocery store. -All of the trees in an orchard were derived from the same rootstock, but half had scion "A" grafted and the other half had a different scion, scion "B," grafted. The trees that were grafted with scion "A" developed large fruits. What characteristics do you think the fruit from the trees that were grafted with scion "B" will have and why?

Which of the following mechanisms of controlling gene expression occurs outside of the nucleus?

The lac operon in Escherichia coli