8. Imagine a population of 1,000 small rodents. Of these, 250 are breeding females, 250 are breeding males, and 500 are nonbreeding juveniles. What is the effective population size?
(A) 1,500
(B) 1,000
(C) 500
(D) 300
(E) 250

4. A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water, equal to the volume of blood lost, is transferred directly into one of his veins. What will be the most probable result of this transfusion? (A) The patient's red blood cells will swell because the blood fluid is hypertonic compared to the cells. (B) The patient's red blood cells will swell because the blood fluid is hypotonic compared to the cells. (C) The patient's red blood cells will shrivel up because the blood fluid is hypertonic compared to the cells. (D) The patient's red blood cells will burst because the blood fluid is hypertonic compared to the cells. (E) It will have no unfavorable effect as long as the water is free of viruses and bacteria.

5. One successful form of gene therapy has involved delivery of an allele for the enzyme adenosine deaminase (ADA) to bone marrow cells of a child with SCID, and delivery of these engineered cells back to the bone marrow of the affected child. What is one major reason for the success of this procedure as opposed to many other efforts at gene therapy? (A) The ADA introduced allele causes all other ADA-negative cells to die. (B) The engineered cells, when reintroduced into the patient, find their way back to the bone marrow. (C) No vector is required to introduce the allele into ADA-negative cells. (D) The immune system fails to recognize cells with the variant gene. (E) The engineered bone marrow cells from this patient can be used for any other SCID patient.

6. If a person drinks a large amount of water in a short period of time, he or she may die from water toxicity. Antidiuretic hormone can help to prevent water retention through interaction with target cells in the (A) bladder. (B) urethra. (C) adrenal gland. (D) kidney. (E) anterior pituitary.

7. A researcher is using adult stem cells and comparing them to other adult cells from the same tissue. Which of the following is a likely finding? (A) The two kinds of cells have virtually identical gene expression patterns in microarrays. (B) The non-stem cells have fewer repressed genes. (C) The non-stem cells have lost the promoters for more genes. (D) The cells from the two sources exhibit different patterns of DNA methylation. (E) Adult stem cells have more DNA nucleotides than their counterparts.

9. In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation? (A) Single-strand binding protein could not bind to the unwound parental strands. (B) Replication fork will be formed. (C) The DNA will supercoil. (D) Replication will occur via RNA polymerase alone. (E) Replication will require a DNA template from another source.

10. A geneticist introduces a transgene into human cells and isolates five independent cell lines in which the transgene has integrated into the human genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Which is a likely explanation for the lack of transgene expression in the fifth cell line? (A) The transgene was mutated during the process of integration into the host cell genome. (B) A transgene integrated into a euchromatic region of the genome. (C) A transgene integrated into a heterochromatic region of the genome. (D) The host cell lacks the enzymes necessary to express the transgene. (E) A transgene integrated into a region of the genome characterized by high histone acetylation.

11. A covalent chemical bond is one in which (A) electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged. (B) protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms. (C) the inner-shell electrons of one atom are transferred to the outer shell of another atom. (D) outer-shell electrons of one atom are transferred to the inner electron shells of another atom. (E) outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms.

12. Melatonin is a hormone produced in the pineal gland. It can be used to treat symptoms of sleep disorders and seasonal affective disorder because (A) it decreases production of serotonin. (B) it increases production of serotonin. (C) it increases production of tryptophan. (D) it activates the brainstem. (E) its peak production is normally at night.

13. If the Sun were to suddenly stop providing energy to the Earth, most ecosystems would vanish. Which of the following ecosystems would likely survive the longest after this hypothetical disaster? (A) desert (B) tropical rainforest (C) tundra (D) benthic ocean (E) grassland

14. Which sequence of blood flow can be observed in either a reptile or a mammal? (A) left ventricle → aorta → lungs → systemic circulation (B) vena cava → right atrium → ventricle → pulmonary circuit (C) right ventricle → pulmonary vein → pulmocutaneous circulation (D) pulmonary vein → left atrium → ventricle → pulmonary circuit (E) right atrium → pulmonary artery → left atrium → ventricle