AP Biology Molecular Heredity #5

Organisms share many conserved core processes and features, including transcription and translation using a uniform genetic code. Scientists have used these shared processes and features in biotechnology. For example, for the process of some transformations, a plasmid is constructed when a eukaryotic gene of interest is added with an antibiotic resistant gene such as beta-lactamase, which is used for antibiotic resistance. This plasmid is then inserted into a prokaryotic bacterial cell, such as E-coli through a transformation process that leads to the production of the product protein from the eukaryotic organism. To culture the bacteria and obtain the protein product, the bacteria must grow. Select the appropriate condition to determine if the plasmid has entered the E-coli bacterial cell.

• nutrient broth to which no antibiotic has been added

• water to which ampicillin has been added.

• nutrient broth to which ampicillin has been added

• nutrient broth to which other resistant bacteria have been added.

Which of the following problems with animal cloning might result in premature death of the clones?

• abnormal gene regulation due to variant methylation

• use of pluripotent instead of totipotent stem cells

• use of nuclear DNA as well as mtDNA

• abnormal immune function due to bone marrow dysfunction

Reproductive cloning of human embryos is generally considered unethical. However, on the subject of therapeutic cloning there is a wider divergence of opinion. Which of the following is a likely explanation?

• use of adult stem cells is likely to produce more types than use of embryonic stem cells

• A clone that lives until the blastocyst stage does not yet have human DNA.

• Cloning to produce embryonic stem cells may lead to great medical benefits for many.

• Cloning to produce stem cells relies on a different initial procedure than reproductive cloning.

Which of the following is true of embryonic stem cells but not of adult stem cells?

• They can give rise to all cell types in the organism.

• They normally differentiate into only eggs and sperm

• One aim of using them is to provide cells for repair of diseased tissue.

• THey can continue to reproduce for an indefinite period.

A researcher is using adult stem cells and comparing them to other adult stem cells from the same tissue. Which of the following is a likely finding?

• THe nonstem cells have lost the promoters for more genes.

• The two kinds of cells have virtually identical gene expression patterns in microarrays.

• The nonstem cells have fewer repressed genes.

• The cells from the two sources exhibit different patterns of DNA methylation.

The first cloned cat, called Carbon Copy, was a calico, but she looked significantly different from her female parent. Why?

• The telomeres of the parent's chromosomes were shorter than those of an embryo.

• Cloned animals have been found to have a higher frequency of transposon activity.

• Fur color genes in cats are influenced by different acetylation patterns.

• X inactivation in the embryo is random and produces different patterns.

Let us suppose that someone is successful at producing induced pluripotent stem cells (iPS) for replacement of pancreatic insulin-producing cells for people with type I diabetes. Which of the following could still be problematic?

I. the possibility that once introduced into the patient, the iPS cells could produce non-pancreatic cells.

II. the failure of the iPS cells to take up residence in the pancreas.

III. the inability of the iPS cells to respond to appropriate regulatory signals.

• II only

• I only

• III only

• all of them

For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. THey decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

• Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.

• Amino acids, (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

• Although there are no more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.

• There is no radioactive isotope of nitrogen.

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). THese two classes of DNA probably represent

• lagging strands and Okazaki fragments

• Okazaki fragments and RNA primers

• leading strands and RNA primers

• Leading strands and Okazaki fragments.

A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grown overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics.

Bacteria that contain the plasmid, but not the eukaryotic gene would grow

• in all four types of broth

• in the nutrient broth without antibiotics only

• in the broth containing tetracycline, but not in the broth containing ampicillin.

• only in the broth containing both antibiotics.