Multiple Choice
In DNA structure, which set correctly lists the four nitrogenous bases found in DNA?
34
views
7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the DNA double helix, what feature makes the two strands antiparallel?
A
The major and minor grooves are produced because the strands run parallel and twist at different rates
B
Hydrogen bonds between bases can only form if both strands have identical sequences in the same orientation
C
Complementary base pairing (A with T and G with C) forces both strands to run in the same direction
D
The two sugar-phosphate backbones run in opposite chemical directions because one strand is oriented and the other is oriented based on their phosphodiester linkages
Verified step by step guidance1
Understand that DNA strands have a directionality based on the chemical structure of their sugar-phosphate backbone. Each strand has a 5' end and a 3' end, referring to the carbon numbers in the sugar molecule.
Recognize that the phosphodiester bonds link the 3' carbon of one sugar to the 5' carbon of the next sugar, giving each strand a specific orientation from 5' to 3'.
Note that in the DNA double helix, the two strands run in opposite directions, meaning one strand runs 5' to 3' while the complementary strand runs 3' to 5'. This opposite orientation is what is meant by 'antiparallel'.
Understand that this antiparallel arrangement is crucial for complementary base pairing (A with T and G with C) and for the formation of hydrogen bonds between bases, which stabilize the double helix.
Conclude that the antiparallel nature arises because the two sugar-phosphate backbones run in opposite chemical directions due to their phosphodiester linkages, not because the strands run parallel or have identical sequences in the same orientation.
Related Videos
Related Practice
