Molecular biologyLesson 1 of 5 in the course Molecular Biology

DNA Structure, RNA Differences, and Chromosome Packaging

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

DNA stores biological information, and its structure helps explain how that information can be copied and used. This lesson examines the evidence that helped scientists determine DNA’s structure, the components of a DNA nucleotide, and how two strands form a double helix.

In the 1950s, James Watson and Francis Crick worked at the University of Cambridge to determine DNA’s structure. They drew on findings from other scientists. Linus Pauling had used X-ray crystallography to investigate protein structures. Maurice Wilkins and researcher Rosalind Franklin were also studying DNA using this method.

All flashcards

What is a DNA nucleotide?
A DNA nucleotide is a building block of DNA made of deoxyribose, a phosphate group, and one nitrogenous base.
Which bases pair in DNA, and how many hydrogen bonds join each pair?
Adenine pairs with thymine through two hydrogen bonds; guanine pairs with cytosine through three hydrogen bonds.
What does antiparallel mean for DNA strands?
The two strands run in opposite orientations: one runs 5′ to 3′ and the other runs 3′ to 5′.
What are purines and pyrimidines in DNA?
Purines are the double-ring bases adenine and guanine. Pyrimidines are the single-ring bases cytosine and thymine.
How did X-ray crystallography contribute to understanding DNA?
It produced patterns from X-rays passing through crystals that revealed clues about molecular structure. Rosalind Franklin’s DNA data helped Watson and Crick develop their structural model.

Quiz questions

  1. Which base does RNA use in place of thymine?Answer: Uracil.
  2. Which type of RNA helps bring amino acids to the machinery assembling a protein?Answer: Transfer RNA (tRNA).
  3. What is the cytoplasmic region containing most prokaryotic DNA called?Answer: The nucleoid.
  4. What structure forms when DNA wraps around histone protein cores?Answer: Nucleosomes.
  5. What form does the DNA molecule in each eukaryotic chromosome take?Answer: A linear DNA molecule.

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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