List The Base Pairing Rules
five.four: Base Pairing in DNA and RNA
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Rules of Base Pairing
The rules of base pairing (or nucleotide pairing) are:
- A with T: the purine adenine (A) e'er pairs with the pyrimidine thymine (T)
- C with G: the pyrimidine cytosine (C) ever pairs with the purine guanine (Chiliad)
This is consistent with in that location not beingness enough space (twenty Å) for 2 purines to fit within the helix and also much infinite for two pyrimidines to get shut enough to each other to form hydrogen bonds betwixt them. Simply why not A with C and G with T? The answer: only with A & T and with C & G are at that place opportunities to establish hydrogen bonds (shown here every bit dotted lines) betwixt them (two between A & T; three between C & G). These relationships are often called the rules of Watson-Crick base of operations pairing, named after the two scientists who discovered their structural ground.
| Organism | A | T | G | C |
|---|---|---|---|---|
| Human | 30.9 | 29.4 | xix.9 | 19.8 |
| Chicken | 28.viii | 29.2 | 20.five | 21.5 |
| Grasshopper | 29.3 | 29.3 | 20.five | twenty.7 |
| Sea Urchin | 32.viii | 32.1 | 17.7 | 17.three |
| Wheat | 27.3 | 27.1 | 22.7 | 22.8 |
| Yeast | 31.3 | 32.nine | 18.seven | 17.1 |
| E. coli | 24.7 | 23.six | 26.0 | 25.vii |
The rules of base of operations pairing tell us that if nosotros can "read" the sequence of nucleotides on i strand of DNA, we can immediately deduce the complementary sequence on the other strand. The rules of base pairing explain the phenomenon that whatever the corporeality of adenine (A) in the Dna of an organism, the amount of thymine (T) is the same (called Chargaff's rule). Similarly, whatever the amount of guanine (G), the corporeality of cytosine (C) is the same. The C+G:A+T ratio varies from organism to organism, particularly among the bacteria, but within the limits of the experimental error, A=T and C=G.
List The Base Pairing Rules,
Source: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book:_Biology_%28Kimball%29/05:_DNA/5.04:_Base_Pairing_in_DNA_and_RNA
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