Question

covalent bonds, weak hydrogen bonds can be easily broken.
sugar-phosphate \backbone\, deoxyribose sugar, covalent bond, phosphate group, hydrogen bond, nitrogenous bases: a - adenine, t - thymine, g - guanine, c - cytosine (dna diagram)
complete the paragraph.
options: weak covalent, strong covalent, weak hydrogen, nitrogenous bases, strong hydrogen, deoxyribose sugars
the structure of a dna molecule resembles a twisted ladder. the rungs of the ladder are formed by □ bonds between the □. the sides of the ladder, or the backbones of the molecule, are formed by □ bonds between the phosphate groups and the □.

Explanation:

• For the rungs: In DNA, the nitrogenous bases (A - T, G - C) are connected by hydrogen bonds, and these bonds are weak (allowing DNA to unzip for replication/transcription).
• For the sides: The sugar - phosphate backbone (deoxyribose sugar and phosphate group) is held together by strong covalent bonds, which provide structural stability to the DNA molecule.

Answer:

1. The rungs of the ladder are formed by $\boldsymbol{\text{weak hydrogen}}$ bonds between the $\boldsymbol{\text{nitrogenous bases}}$.
2. The sides of the ladder are formed by $\boldsymbol{\text{strong covalent}}$ bonds between the phosphate groups and the $\boldsymbol{\text{deoxyribose sugars}}$.