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Which of the following represents the complementary strand of a DNA sequence 3' TCGATCGCA 5'?

A. 3' AGCTAGCGT 5'

B. 5’ AGCTAGCGT 3’

C. 5' UCGAUCGCA 3'

D. 3' TCGUTCGCU 3'

Answer Explanation:

In DNA, the nitrogenous bases adenine (A) and thymine (T) pair together, while cytosine (C) and guanine (G) pair together.

Therefore, the complementary strand of the given DNA sequence 3' TCGATCGCA 5' would have the complementary nitrogenous bases as:

5’ AGCTAGCGT 3’

NOTE: The 5’ to 3’ direction of the complementary strand is opposite to that of the given strand.

Choice A.

3’ AGCTAGCGT 5’ is not correct because it is not complementary to the given strand.

Choice C.

5’ UCGAUCGCA 3’ is not correct because it contains uracil (U), which is a nitrogenous base found in RNA, not DNA.

Choice D.

3’ TCGUTCGCU 3’ is not correct because it also contains uracil (U), which is a nitrogenous base found in RNA, not DNA.

 

Therefore, the Correct Answer is B.

More Questions on TEAS 7 Science

  • Q #1: Which of the following allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host cell after the AIDS virus enters the cell?

    A. The phospholipids found on the envelope of the virus.

    B. Reverse transcriptase, an enzyme encoded by the virus.

    C. Receptor proteins located on the surface of the virus.

    D. The protein that makes up the capsid of the virus.

    Answer Explanation

    Reverse transcriptase, an enzyme encoded by the virus.

    Reverse transcriptase is a virus-specific enzyme that transcribes an RNA template to DNA1.

    This allows the AIDS virus, which contains RNA, to insert viral DNA into the DNA of a host cell after the AIDS virus enters the cell.

     

    Choice A, The phospholipids found on the envelope of the virus, is not the correct answer because phospholipids are a major component of cell membranes and do not play a direct role in inserting viral DNA into the DNA of a host cell.

    Choice C, Receptor proteins located on the surface of the virus, is not the correct answer because receptor proteins located on the surface of the virus play a role in attachment and fusion of HIV virons to host cells, but do not play a direct role in inserting viral DNA into the DNA of a host cell.

    Choice D, The protein that makes up the capsid of the virus, is not the correct answer because capsid is the outer protein shell of a virus and does not play a direct role in inserting viral DNA into the DNA of a host cell.

  • Q #2: Which of the following substances is responsible for donating H+ ions to act as a buffer when blood pH rises?  

    A. Carbon dioxide

    B. Carbon monoxide

    C. Carbonic acid

    D. Oxygen

    Answer Explanation

    Carbonic acid.

    In the human body, maintaining the pH of the blood within a narrow range is critical for proper physiological functioning.

    One of the buffering systems that helps to regulate blood pH involves the conversion of carbon dioxide (CO2) and water (H2O) into carbonic acid (H2CO3), which then dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).

     

    Carbonic acid (H2CO3) is responsible for donating H+ ions to act as a buffer when blood pH rises.

    When blood pH rises (becomes more alkaline), carbonic acid dissociates, and the H+ ions combine with bicarbonate ions to form more carbonic acid.

    This helps to remove excess H+ ions from the blood and prevent the pH from rising too much.

    Option A, carbon dioxide, is involved in the buffering system through its conversion to carbonic acid.

    However, it does not directly donate H+ ions to act as a buffer when blood pH rises.

    Option B, carbon monoxide, is a toxic gas that binds to hemoglobin in red blood cells, preventing them from carrying oxygen.

    It is not involved in the buffering system and does not donate H+ ions.

    Option D, oxygen, is carried by hemoglobin in red blood cells and is essential for respiration.

    It is not involved in the buffering system and does not donate H+ ions.

  • Q #3: Hikers who found a human body at high altitude in the Italian Alps thought the man had died recently, but tests indicated he was shot with an arrow more than 5,300 years ago. Which of the following would be the best reason for prolonged preservation of the body? .

    A. The food that the person ate contained toxins that killed the bacteria that would have otherwise destroyed the body

    B. The arrow wound caused blood to flow out of the body, which led the enzymes that would break down tissue to be cleared from the body

    C. The body was frozen in the cold temperature of the Alps shortly after he died and remained frozen until it was found

    D. The ultraviolet rays at such a high altitude caused all the body's molecules to be preserved.

    Answer Explanation

    The best reason for the prolonged preservation of the body is that it was frozen in the cold temperature of the Alps shortly after he died and remained frozen until it was found.

    Freezing can preserve a body by slowing down or stopping the decomposition process.

    Choice A is not correct because the food that the person ate would not have contained toxins that killed the bacteria that would have otherwise destroyed the body.

    Choice B is not correct because the arrow wound would not have caused blood to flow out of the body in a way that would have cleared enzymes that break down tissue from the body.

    Choice D is not correct because ultraviolet rays at high altitude would not have caused all of the body’s molecules to be preserved.