Multiple Choice
Why did Phoebus Levene propose that proteins, rather than DNA, were the genetic material of cells?
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14. DNA Synthesis
Discovering the Structure of DNA
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Which of the following describes a DNA-binding motif?
A
Zinc finger
B
Helix-turn-helix
C
Alpha helix
D
Beta sheet
Verified step by step guidance1
Understand that a DNA-binding motif is a structural domain within a protein that interacts with DNA sequences.
Recognize that the 'helix-turn-helix' motif is a common structural motif capable of binding DNA, often found in transcription factors.
Identify the structure of the 'helix-turn-helix' motif: it consists of two α-helices connected by a short sequence of amino acids that make the 'turn'.
Differentiate between the options: 'zinc finger', 'alpha helix', and 'beta sheet'. Note that 'zinc finger' is another type of DNA-binding motif, but 'alpha helix' and 'beta sheet' are general protein secondary structures not specific to DNA binding.
Conclude that the 'helix-turn-helix' is the correct answer as it specifically describes a DNA-binding motif, characterized by its ability to fit into the major groove of DNA and facilitate specific interactions.
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