An individual is born with a mutation causing her to partially retain a form of fetal hemoglobin into adulthood.Compared to a normal individual, this person would exhibit:
Answer(s): D
Fetal hemoglobin has a higher affinity for oxygen than does adult hemoglobin. Thus, it binds and holds oxygen more tightly. An individual with fetal hemoglobin would show increased oxygen binding to hemoglobin as a result.A false, because fetal and adult hemoglobin are different.B false, because fetal hemoglobin binds more to oxygen, not less.C false. In fact, reactivating fetal hemoglobin can be used as a treatment for sickle-cell.
For a particular plant, straight leaves result from a dominant gene (L) and wrinkled leaves result from a recessive gene (l), and tall height results from a dominant gene (T) while short height results from a recessive gene (t). A dihybrid cross is performed with plants heterozygous for both traits. What is the expected ratio of short, straight-leaved plants to tall, straight-leaved plants?
Answer(s): C
In a dihybrid cross, the genes for two traits are crossed in a Punnett square. For two heterozygotes crossed in a Punnett square, the expected ratio of recessive/recessive, dominant/recessive, recessive/dominant, to dominant is 1:3:3:9. In this particular question, the ratio of both recessive/dominant to dominant/dominant is1:3.
The lining of the digestive tract and the respiratory tract develops from which germ layer?I). EndodermII). MesodermIII). Ectoderm
Answer(s): A
The lining of the digestive tract and the respiratory tract develops from the endoderm. As a rule of thumb for the MCAT, think of the fetus developing from a tube. Skin and nervous systems develop from ectoderm (outside of tube), digestive tract and respiratory tract from endoderm (inside of tube), and cardiovascular, skeletal, and muscle tissues develop from mesoderm (in-between outside and inside of tube). On MCAT questions, tissues will almost always develop from one germ-layer only.
Which of the following molecules will stop being produced first when oxygen is no longer supplied to the cell?
This question is testing your understanding of the utilization of oxygen in the production of metabolic energy.Under aerobic conditions, oxygen serves as the final electron accepter in the electron transport chain, which yields water and ATP as final products. In the absence of oxygen, the cell switches from aerobic respiration to anaerobic respiration. As a result, the ETC chain will stop functioning and water will no longer be produced.Oxaloacetate (choice A), an intermediate in the citric acid cycle, is controlled by negative feedback from the ETC. Therefore, the production of oxaloacetate will eventually stop, but the production of water will stop first.Thus, C is the best answer. Without ATP production occurring via aerobic respiration, anaerobic respiration will become the source of ATP for the cell. As a result, glycolysis will increase in order to meet the energy requirements of the cell resulting in an increase in pyruvate (choice B), a product of glycolysis.
All of the following are true regarding the function of neurons EXCEPT:
This question is testing your understanding of the function of action potentials and neuronal transmission of signals. Here, (A), (B), and (D) are all true. Since this is an "EXCEPT" question, the right answer is the one false statement: choice (C). A neuron secretes neurotransmitters from its axon, not its dendrites.
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