What types of linkage joins the nucleotides a) within a single DNA strand and b) between two single DNA strands?
There is quite a bit of reading here but I think your answers are here. http://en.wikipedia.org/wiki/DNA
a) The linkage that joins nucleotides within a single DNA strand is called a phosphodiester bond. To understand it, let's break it down:
1. Start with the DNA structure: DNA is made up of a double helix structure consisting of two strands that are complementary to each other. Each strand is composed of a chain of nucleotides.
2. Nucleotide structure: Each nucleotide consists of three components: a phosphate group, a sugar molecule (deoxyribose in DNA), and a nitrogenous base (adenine, thymine, cytosine, or guanine).
3. Formation of phosphodiester bond: The phosphodiester bond is formed when the phosphate group of one nucleotide forms a bond with the sugar molecule (specifically the 3' carbon) of the next nucleotide in the same DNA strand. This bond is formed through a condensation reaction, where a water molecule is released.
b) The linkage that joins nucleotides between two single DNA strands is called hydrogen bonding. Here's how it works:
1. Complementary base pairing: In DNA, adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). These pairs are held together by hydrogen bonds.
2. Hydrogen bonding: Hydrogen bonds are weak electrostatic attractions between a hydrogen atom and an electronegative atom (in this case, nitrogen atoms in the bases). Each adenine forms two hydrogen bonds with thymine, and each cytosine forms three hydrogen bonds with guanine.
3. Stability of the double helix: The hydrogen bonds between the base pairs contribute to the stability of the DNA double helix structure. They help hold the two DNA strands together by forming a complementary bond between the bases.
In summary, phosphodiester bonds link nucleotides within a single DNA strand, while hydrogen bonds connect nucleotides between two DNA strands.