Question

in a single organism, what do you notice about the relative proportions of dna bases?
a and t occur in similar proportions.
t and g occur in similar proportions.
a and c occur in similar proportions.
g and c occur in similar proportions.
done

Explanation:

According to Chargaff's rules, in DNA, adenine (A) pairs with thymine (T) through two hydrogen bonds, and guanine (G) pairs with cytosine (C) through three hydrogen bonds. This complementary base - pairing leads to the proportion of A being approximately equal to T, and the proportion of G being approximately equal to C in an organism's DNA. Looking at the data in the table for each organism:

• For humans: \(A = 30.9\%\), \(T=29.4\%\) (close values); \(G = 19.9\%\), \(C = 19.8\%\) (close values)
• For chickens: \(A = 28.8\%\), \(T = 29.2\%\) (close values); \(G=20.5\%\), \(C = 21.5\%\) (close values)
• For grasshoppers: \(A = 29.3\%\), \(T = 29.3\%\) (equal values); \(G = 20.5\%\), \(C=20.7\%\) (close values)
• For sea urchins: \(A = 32.8\%\), \(T = 32.1\%\) (close values); \(G = 17.7\%\), \(C = 17.3\%\) (close values)
• For wheat: \(A = 27.3\%\), \(T = 27.1\%\) (close values); \(G = 22.7\%\), \(C = 22.8\%\) (close values)
• For yeast: \(A = 31.3\%\), \(T = 32.9\%\) (relatively close values considering biological variation); \(G = 18.7\%\), \(C = 17.1\%\) (relatively close values considering biological variation)
• For E.coli: \(A = 24.7\%\), \(T = 23.6\%\) (relatively close values considering biological variation); \(G = 26.0\%\), \(C = 25.7\%\) (relatively close values considering biological variation)

Answer:

A. A and T occur in similar proportions.
D. G and C occur in similar proportions.