When analyzing the relative proportions of DNA bases (Adenine [A], Thymine [T], Guanine [G], and Cytosine [C]) across various organisms, we can draw several observations and trends.
Let's begin by examining the data provided:
[tex]\[
\begin{array}{|c|c|c|c|c|}
\hline \multicolumn{5}{|c|}{\text{Relative Proportions (\%) of Bases in DNA}} \\
\hline \text{Organism} & \text{A} & \text{T} & \text{G} & \text{C} \\
\hline \text{Human} & 30.9 & 29.4 & 19.9 & 19.8 \\
\hline \text{Chicken} & 28.8 & 29.2 & 20.5 & 21.5 \\
\hline \text{Grasshopper} & 29.3 & 29.3 & 20.5 & 20.7 \\
\hline \text{Sea urchin} & 32.8 & 32.1 & 17.7 & 17.3 \\
\hline \text{Wheat} & 27.3 & 27.1 & 22.7 & 22.8 \\
\hline \text{Yeast} & 31.3 & 32.9 & 18.7 & 17.1 \\
\hline \text{E. coli} & 24.7 & 23.6 & 26.0 & 25.7 \\
\hline
\end{array}
\][/tex]
### Trends and Similarities:
1. Complementarity of A and T, G and C:
- Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).
- We generally observe that the proportions of A are quite similar to those of T, and similarly, G is close to C in each organism. This is consistent with the base-pairing rules of DNA.
2. Closely Related Organisms:
- Chicken and Grasshopper:
- Chicken: [tex]\(A = 28.8\%, T = 29.2\%, G = 20.5\%, C = 21.5\%\)[/tex]
- Grasshopper: [tex]\(A = 29.3\%, T = 29.3\%, G = 20.5\%, C = 20.7\%\)[/tex]
- Both organisms have very close proportions in A, T, G, and C, indicating a possible closer evolutionary relationship or similar adaptations.
3. Higher Organisms (Eukaryotes) vs. Bacteria:
- Eukaryotes (such as humans, chickens, and plants like wheat) have more varied proportions compared to a bacterium like E. coli.
- Human: [tex]\(A = 30.9\%, T = 29.4\%, G = 19.9\%, C = 19.8\%\)[/tex]
- E. coli: [tex]\(A = 24.7\%, T = 23.6\%, G = 26.0\%, C = 25.7\%\)[/tex]
- E. coli has a significantly higher proportion of G and C compared to A and T, which is different from most higher organisms.
4. Trends in Specific Groups:
- Humans, Chickens, and Grasshoppers:
- These organisms maintain relatively similar proportions where A and T range in the high 20s to low 30s, and G and C are around 19-21%.
- Plants and Fungi:
- Wheat: [tex]\(A = 27.3\%, T = 27.1\%, G = 22.7\%, C = 22.8\%\)[/tex]
- Yeast: [tex]\(A = 31.3\%, T = 32.9\%, G = 18.7\%, C = 17.1\%\)[/tex]
- These have more G and C in wheat compared to yeast where A and T are more pronounced.
### Conclusion:
The proportions of DNA bases vary significantly among different species. Similarities are often noticeable among closely related species, with more distinct differences observable in more distantly related organisms. However, the general trend of base-pair complementarity (A with T, and G with C) holds true across all organisms.
Therefore, while there are similarities in the proportions of DNA bases within certain groups of organisms, significant variability exists, especially when comparing more distantly related species.
