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Suddenly I became aware that an adenine-thymine pair held together by two hydrogen bonds was identical in shape to a guanine-cytosine pair held together by at least two hydrogen bonds. All the hydrogen bonds seemed to form naturally; no fudging was required to make the two types of base pairs identical in shape.

[…]

The hydrogen-bonding requirement meant that adenine would always pair with thymine, while guanine could pair only with cytosine. Chargaff’s rules then suddenly stood out as a consequence of a double-helical structure for DNA. Even more exciting, this type of double helix suggested a replication scheme much more satisfactory than my briefly considered like-with-like pairing.

Explanation and Analysis:

The day after confirming that the two strands of DNA cannot possibly have the same sequence of bases, Watson returned to the drawing board to look for a way to fit different nitrogenous bases together. He quickly realized that just as adenine, ...

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Original

Romeo

(aside) She speaks.
O, speak again, bright angel! For thou art
As glorious to this night, being o’er my head,
As is a winged messenger of heaven
Unto the white, upturnèd, wondering eyes
Of mortals that fall back to gaze on him
When he bestrides the lazy-puffing clouds
And sails upon the bosom of the air.

Juliet

O Romeo, Romeo! Wherefore art though Romeo?
Deny they father and refuse they name.
Or, if thou wilt not, be but sworn my love,
And I’ll no longer be a Capulet.

Modern

Romeo

(to himself) She speaks. Speak again, bright angel! For tonight you are as glorious, there up above me, as a winged messenger of heaven who makes mortals fall onto their backs to gaze up with awestruck eyes as he strides across the lazy clouds and sails through the air.

Juliet

O Romeo, Romeo! Why must you be Romeo? Deny your father and give up your name. Or, if you won’t change your name, just swear your love to me and I’ll give up being a Capulet.

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