Module 7 Molecular Genetics

3.7.1 page 3

Lesson Summary

The discovery of DNA being the molecule responsible for heredity and the structural characteristics of DNA go hand in hand. Once scientists could see, and were able to closely examine, the structure of DNA, it became obvious that this molecule had to be responsible for passing our genetic information on to the next generation. Throughout this lesson you have learned about some of the many scientists that contributed to solving these scientific questions. Every experiment and discovery built on the last, pushing forward toward the eventual result – the structure and function of DNA. The double helix that Watson and Crick modeled would not have been possible without the x-ray image from Rosalind Franklin.  The complementary base pairing in Watson and Crick’s model may not even have been thought up without the information from Phoebus Levene and his identification of the four nucleotides and their respective percent compositions. In this lesson, you have learned about the history of the identification of DNA and the structure of DNA. In the next lesson you will see how DNA’s structure directly determines its function.

Glossary

Antiparallel: describes the property by which the 5’ to 3’ phosphate bridges run in opposite directions on each strand of nucleotides in a double-stranded DNA molecule

Chargaff’s Rule:  in any sample of DNA, a constant relationship in which the amount of adenine is always approximately equal to the amount of thymine, and the amount of cytosine is always approximately equal to the amount of guanine

Complementary base pairs: refers to the hydrogen bonded, nitrogenous base pairs of adenosine and thymine, and of cytosine and guanine in the DNA double helix

DNA: deoxyribonucleic acid (DNA), a double-stranded nucleic acid molecule that governs the processes of heredity in the cells of all organisms: composed of nucleotides containing a phosphate group, a nitrogenous base and deoxyribose

Double-helix: spiral shape most commonly associated with DNA, made up of two long strands of nucleotides bound together and twisted