Question

share out/discussion (5 minutes)

1. the proportions of the bases are consistent within a species; however they do vary between species.

using the base - pair rules, complete the following table to show the percentage of each type of base in the five different organisms.

Explanation:

Step1: Apply Chargaff's rule

According to Chargaff's rule, in DNA, \(A = T\) (adenine equals thymine) and \(G = C\) (guanine equals cytosine), and \(A+T + G + C=100\%\).

Step2: Calculate for Wheat

For wheat, since \(A = 27\%\), then \(T=27\%\). So \(G + C=100-(27 + 27)=46\%\). Since \(G = C\), then \(G = C=\frac{46}{2}=23\%\).

Step3: Calculate for Salmon

For salmon, \(G + C=100-(29 + 21)=50\%\). Since \(G = C\), then \(G = C = 25\%\).

Step4: Calculate for Cow

For cow, since \(A = 28\%\), then \(T = 28\%\). So \(G + C=100-(28+28)=44\%\). Since \(G = C\), then \(G = C=\frac{44}{2}=22\%\).

Step5: Calculate for Yeast

For yeast, since \(A = 31\%\), then \(T = 31\%\). So \(G + C=100-(31 + 31)=38\%\). Since \(G = C\), then \(G = C=\frac{38}{2}=19\%\).

Answer:

Organism	Adenine	Guanine	Cytosine	Thymine
Wheat	27	23	23	27
Salmon	21	25	25	29
Cow	28	22	22	28
Human	31	19	19	31