Calculate the number of phosphodiester bonds and hydrogen bonds in a 100 base pair dsDNA molecule where 40% of the bases are Guanine.

A dsDNA molecule with 100 base pairs means it has two strands, and each strand contains 100 nucleotides.
In a linear DNA strand with $n$ nucleotides, there are $n-1$ phosphodiester bonds.
For each strand:
Number of phosphodiester bonds per strand = $100 - 1 = 99$ bonds.
Since there are two strands in a dsDNA molecule:
Total phosphodiester bonds = $99 \text{ (strand 1)} + 99 \text{ (strand 2)} = 198$ bonds.

The dsDNA molecule has 100 base pairs, which means a total of $100 \times 2 = 200$ bases.
We are given that 40% of the bases are Guanine (G).
Number of Guanine (G) bases = $0.40 \times 200 = 80$ bases.
According to Chargaff's rules, in dsDNA, the number of Guanine (G) bases equals the number of Cytosine (C) bases.
Number of Cytosine (C) bases = 80 bases.
Total G and C bases = $80 + 80 = 160$ bases.
The remaining bases are Adenine (A) and Thymine (T).
Number of A and T bases = Total bases - (G + C) bases = $200 - 160 = 40$ bases.
Since the number of Adenine (A) bases equals the number of Thymine (T) bases:
Number of Adenine (A) bases = $40 / 2 = 20$ bases.
Number of Thymine (T) bases = $40 / 2 = 20$ bases.

Now, we calculate the hydrogen bonds:

• Guanine (G) forms 3 hydrogen bonds with Cytosine (C).
• Adenine (A) forms 2 hydrogen bonds with Thymine (T).

Hydrogen bonds from G-C pairs = Number of G bases $\times$ 3 = $80 \times 3 = 240$ hydrogen bonds.
Hydrogen bonds from A-T pairs = Number of A bases $\times$ 2 = $20 \times 2 = 40$ hydrogen bonds.
Total hydrogen bonds = $240 + 40 = 280$ hydrogen bonds.

Therefore, the total number of phosphodiester bonds is 198, and the total number of hydrogen bonds is 280.

Comparing this with the given options:
A) 198 and 280
B) 198 and 240
C) 200 and 280
D) 200 and 240

The correct option is A.

The final answer is $\boxed{\text{A) 198 and 280}}$