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Ch. 9 - DNA Structure and Analysis
Klug - Essentials of Genetics 10th Edition
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Not the one you use?Change textbook
Chapter 9, Problem 27a

A primitive eukaryote was discovered that displayed a unique nucleic acid as its genetic material. Analysis provided the following information:
The general X-ray diffraction pattern is similar to that of DNA, but with somewhat different dimensions and more irregularity.

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1
Step 1: Understand the context of the problem by recognizing that the organism's genetic material shows an X-ray diffraction pattern similar to DNA, which suggests a helical structure but with differences in dimensions and regularity.
Step 2: Recall that DNA's X-ray diffraction pattern is characterized by a regular, repeating helical structure, typically producing a distinct 'X' shape pattern due to its uniformity and consistent dimensions.
Step 3: Consider what differences in dimensions and irregularity might imply about the nucleic acid structure, such as variations in helix pitch, diameter, or base pairing that could affect the diffraction pattern.
Step 4: Analyze how these structural differences could influence the biological properties of the nucleic acid, including stability, replication, and interaction with proteins, by comparing to known DNA and RNA structures.
Step 5: Formulate hypotheses about the nature of this unique nucleic acid, possibly involving alternative sugar backbones, base modifications, or non-standard pairing, and design experiments to further characterize its chemical composition and biological function.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Structure and Properties of DNA

DNA is a double-helical nucleic acid with a regular, repeating structure that produces a characteristic X-ray diffraction pattern. Its dimensions and uniformity are well-studied, serving as a reference for identifying nucleic acids. Understanding DNA’s structure helps compare and contrast with novel genetic materials.
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DNA Structure

X-ray Diffraction in Molecular Analysis

X-ray diffraction is a technique used to determine the three-dimensional structure of molecules by analyzing the pattern of X-rays scattered by the sample. Differences in diffraction patterns reveal variations in molecular dimensions and regularity, aiding in identifying unique nucleic acid structures.
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X-Inactivation

Genetic Material Diversity in Eukaryotes

While DNA is the common genetic material in eukaryotes, some primitive or unusual organisms may use alternative nucleic acids or modified forms. Recognizing the possibility of unique genetic materials expands understanding of molecular evolution and genetic diversity.
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Eukaryotic Transcription