Maternal lineage can be traced by sequencing the mitochondrial DNA because the mitochondrial genome is derived primarily from the mother. The best Explanation: for this phenomenon is that:
Answer(s): C
Upon penetration of the egg, the sperm mitochondria fall apart and are not replicated when divisions begin.This question can best be answered by eliminating the wrong answer choices.Choice A is incorrect because sperm have large numbers of mitochondria used to drive locomotion.Choice B is incorrect because mitochondria are replicated prior to cell division. Also, this choice would not explain the presence of the maternal genome which should also be diffused by division.Choice D is incorrect because many of the genes coding for mitochondrial proteins are located in the mitochondrial DNA.
The endosymbiosis theory proposes that mitochondria originated through the engulfing of aerobic prokaryotes by anaerobic host prokaryotes. Many of the enzymes required for aerobic respiration are located on the inner membrane of the mitochondriA. Where would these enzymes, or their precursors, most likely have been found three billion years ago (prior to endosymbiosis)?
As the host cell engulfs a prokaryotic aerobic cell, the host cell membrane forms a vesicle about the aerobic cell, giving a double membrane structure. The inner membrane is formed bythe plasma membrane of the aerobic cell.Choice A is incorrect because enzymes in the cytoplasm of the anaerobic host cell would remain in the cytoplasm.Choice B is incorrect because enzymes on the plasma membrane of the anaerobic host cell would befound on the outer membrane of the mitochondria formed by endosymbiosis.Choice D is incorrect because enzymes in the cytoplasm of the aerobic cell would be within the matrix of the mitochondria formed by endosymbiosis.
A mountain climber living at sea level ascends to a very high altitude during the course of a day long climb. By the end of the day, all of the following acclimatizations will occur EXCEPT:
The affinity of hemoglobin for oxygen will not decrease. The adaptation of hemoglobin's affinity for oxygen would take longer than one day. Besides, even if given time to adjust, in order to maintain delivery of oxygen to tissues at high altitudes (low pO2), the affinity of hemoglobin for oxygen would increase so as to maximize the amount of oxygen transported by the hemoglobin in the blood. Choices A, B, and D are incorrect because these are all acclimatizations that occur immediately. The body will make rapid adjustments to the low pO2 of high altitude in order to maintain delivery of oxygen to the tissues. Tidal volume and respiration rate will increase, in order to increase the minute volume (amount of air inhaled and exhaled in a minute). Inhaling more air than normal will compensate for the fact that the inhaled air has less oxygen than normal. In addition, the body will secrete erythropoietin to increase the number of erythrocytes in the blood and thus increase the oxygen carrying capacity of the blood.
At its isoelectric point, an amino acid in an electric field will migrate towards the:
Answer(s): D
At its isoelectric point, an amino acid exists as a zwitterion with positive and negative charges that cancel each other out. Because it has no net charge, it will not migrate in an electric field.
Which of the following species will form the most stable radical?
Answer(s): A
The stability of free radicals decreases from tertiary>secondary>primary>methyl. Choice A is the only choice that can form a tertiary radical.Choices B, C, and D will form secondary radicals.
Post your Comments and Discuss Test Prep MCAT Test exam prep with other Community members:
Our website is free, but we have to fight against AI bots and content theft. We're sorry for the inconvenience caused by these security measures. You can access the rest of the MCAT Test content, but please register or login to continue.