Hydrogen bonds between the orange and red strands are not shown but are implied by the model. True The model shows the correct polarity between the orange and red strands_ True The red lines represent DNA_ True The labels refer to the end of the strand with nitrogenous base. False The model correctly shows an arrowhead on the 3′ ends of the strands_ True The labels refer to the end of the strand with phosphate group: True The orange line represents RNA True
The Correct Answer and Explanation is:
Let’s break down the statements:
- Hydrogen bonds between the orange and red strands are not shown but are implied by the model.
True. In many representations of DNA, hydrogen bonds between complementary bases (e.g., adenine and thymine, cytosine and guanine) are implied by the base pairing rule but are not always explicitly shown in every diagram, especially if it’s a simplified model. - The model shows the correct polarity between the orange and red strands.
True. DNA strands have polarity; one end has a free 5′ phosphate group, and the other has a free 3′ hydroxyl group. In this case, the model should correctly represent the opposite directions of the two strands, which are antiparallel (one runs 5′ to 3′, and the other runs 3′ to 5′). - The red lines represent DNA.
True. Assuming the red lines represent the backbone of the DNA strand (typically the sugar-phosphate backbone), this is correct. The backbone is usually depicted as lines or chains in structural representations of DNA. - The labels refer to the end of the strand with nitrogenous base.
False. The labels likely refer to the ends of the DNA strand with the phosphate group (5′ end) or the hydroxyl group (3′ end), not the nitrogenous bases. Nitrogenous bases (adenine, thymine, cytosine, and guanine) are part of the internal structure of the strand, forming base pairs with the opposite strand. - The model correctly shows an arrowhead on the 3′ ends of the strands.
True. It’s common to indicate the 3′ end of the strand with an arrowhead, since DNA’s directionality is crucial for processes like replication and transcription. The arrowhead should point toward the 3′ end, confirming the strand’s polarity. - The labels refer to the end of the strand with phosphate group.
True. As mentioned, the 5′ end of a DNA strand has a free phosphate group, and in some diagrams, the 5′ end may be labeled with a phosphate group. - The orange line represents RNA.
True. If the orange line represents RNA, this would suggest the model is depicting a strand of RNA (which is single-stranded and uses uracil instead of thymine as a nitrogenous base). This is common in models comparing DNA and RNA structure.
In conclusion, this is a relatively accurate description of a DNA/RNA model showing the essential features and directionality of the strands, with some simplifications like implying the hydrogen bonds between the strands.
