【GR1724】 The Solution for GRE Biology Practice Test [21-40]

The Solution for GRE Biology Practice Test [21-40]

 

추천글 : 【GRE】 Solution for GRE Biology Practice Test 

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21. Which of the following statements about mitochondria and chloroplasts is generally true?

 

 

⑴ answer: E

⑵ Chloroplasts are only existant in plant cells.

 

 

22. The following pairs were placed in solution together. Which two could be separated by performing low-speed centrifugation?

 

 

⑴ answer: B

⑵ 1st centrifugation (1,000g, 10 min) : Nuclei precipitate.

⑶ 2nd centrifugation (3,000g, 10 min) : Chloroplasts precipitate.

⑷ 3rd centrifugation (20,000g, 10 min) : Mitochondria precipitate.

⑷ 4th centrifugation (150,000g, 180 min) : ERs precipitate.

 

 

23. Phalloidin is a toxin made by the death cap mushroom. The toxin binds to actin subunits and disrupts actin function. Which of the following structures would be most directly affected by phallodin?

 

 

⑴ answer: C

⑵ Microflaments are made up of actins and myosins.

 

 

24. Mitochondria isolated and placed in a buffered solution with a low pH begin to manufacture ATP. Which of the following is the best explanation for the effect of low external pH?

 

 

⑴ answer: D

⑵ H⁺ migrates from the intermembrane space (high concentration) to the matrix (low concentration) by simple diffusion.

 

 

25. Which of the following sets of reactions occurs in the stroma of the chloroplast in plant cells?

 

 

⑴ answer: A

⑵ Calvin cycle 

 

 

26. Which of the following is typically NOT found in normal somatic cells of a human male?

 

 

⑴ answer: B

⑵ Bar body (an inactivated X chromosome) only appears in human female for a proper amount of X chromosome RNAs.

 

 

27. Which of the following is the most direct cause of polyteny in somatic cells of certain organisms?

 

 

⑴ answer: C

⑵ polyteny 

 

 

28. In humans, a hereditary disorder called xeroderma pigmentosum (XP) can result in the inability to repair ultraviolet damage to DNA. Which of the following molecular lesions is most likely to accrue in individuals with XP?

 

 

⑴ answer: A

⑵ UV damage is related to thymine dimers.

 

Figure. 1. UV damage and thymine dimers

 

 

29. Portions of the DNA sequences of normal and mutant β-globin genes are shown below. The most plausible explanation for why the indicated mutation (changing an A to a G) results in the disease β-thalassemia is that the mutation

 

 

⑴ answer: C

⑵ There is no change in exon sequence and reading frame, but intron sequence that is related to alternative splicing.

 

 

30. Which of the following is encoded by the src oncogene and catalyzes the specific addition of phosphate groups to cellular proteins?

 

 

⑴ answer: D

 

 

31. Mutation of homeotic cluster genes often results in which of the following developmental defects in Drosophila?

 

 

⑴ answer: B

⑵ Homeo box (HOX) affects organogenesis when being embryo.

 

 

32. Monoclonal antisera are distinguished from polyclonal antisera in which of the following ways?

 

 

⑴ answer: C

⑵ A single matured B cell can secrete an identical antibody.

 

 

33. Which of the following most accurately describes a retrotransposon?

 

 

⑴ answer: C

⑵ transposon : cut and paste

⑶ retrotransposon : copy and paste

 

 

34. Which of the following cells are typically necessary for the production of a maximal humoral response upon initial exposure to a protein antigen?

 

 

⑴ answer: E

⑵ DC : Antigen presenting DC, etc should be involved.

⑶ T lymphocyte : Helper T cell, etc should be involved.

⑷ B lymphocyte : Antigen-processing plasma cell, etc should be involved.

 

 

35. The figure below shows an intact linear DNA segment from two subspecies (lanes X and Y) and the same DNA segments digested by EcoRⅠ (lanes X' and Y'), separated on an electrophoretic gel. Which of the following is the simplest explanation for the difference between the DNA segments of the two subspecies?

 

 

⑴ answer: B

⑵ 720 bp = 540 bp + 180 bp

 

 

36. If the activity of an enzyme is constant over a broad range of pH values, it is likely that

 

 

⑴ answer: D

⑵ If there are ionizing groups including amines, pH-dependent structural changes linked to the activity should be found.

⑶ Not only pH and temperature but also salts affect the activity of an enzyme.

 

 

37. Which of the following developmental processes has been most recently completed in the amphibian embryo shown below?

 

 

⑴ answer: D

⑵ amphibian embryology 

 

 

38. Which of the following plant cells undergoes programmed cell death to become functional?

 

 

⑴ answer: B

⑵ xylem vessel member 

 

 

39. Which of the following provides visual evidence of genetic recombination during meiosis?

 

 

⑴ answer: D

⑵ chiasmata (crossing over)

 

 

40. A plant that possesses swimming sperm, xylem with tracheids, independent gametophyte and sporophyte phases, and no seeds is probably most closely related to 

 

 

⑴ answer: C

 

입력: 2023.05.06 10:41