Chargaff's rule is a fundamental principle in molecular biology that describes the pairing behaviors of bases in DNA. To determine the correct base pairings, let's break down the rule and understand what each option represents.
1. In DNA, Adenine (A) always pairs with Thymine (T).
2. Similarly, Cytosine (C) always pairs with Guanine (G).
This rule ensures that the structure of DNA is maintained consistently. Let's examine the options given:
1. [tex]$A=T ; C=G$[/tex]: This option states that Adenine pairs with Thymine and Cytosine pairs with Guanine. This correctly follows Chargaff's rule as described.
2. [tex]$A=C ; T=G$[/tex]: This option states that Adenine pairs with Cytosine and Thymine pairs with Guanine, which is incorrect according to Chargaff's rule.
3. [tex]$A=G ; T=U$[/tex]: This option states that Adenine pairs with Guanine and Thymine pairs with Uracil. This is incorrect because Adenine does not pair with Guanine in DNA, and Uracil is found in RNA, not DNA.
4. [tex]$A=U ; C=G$[/tex]: This option states that Adenine pairs with Uracil and Cytosine pairs with Guanine. This partially follows Chargaff's rule for Cytosine and Guanine, but Uracil is not found in DNA; it is a component of RNA.
After evaluating each option based on Chargaff's rule, the correct answer is:
[tex]$A=T ; C=G$[/tex]
