How do the nitrogen bases pairs join in dna?

There are 4 nitrogenous bases in DNA. Adenine pairs with thymine, and Guanine pairs with cytosine. A Dna Nucleotide consists of a 5 carbon sugar, a phosphate group and a nitrogenous base. These bases are paired up by weak hydrogen bonds, so when they have have to replicate, the enzyme helicase can easily unzip the Dna. 

Twins are born minutes apart, not a year apart. fraternal twins are no more closely related genetically than ordinary siblings born a year apart. they just happen to be born at the same time. identical twins result from a single fertilized egg dividing and separating early in gestation. although identical twins are more similar to each other than other siblings, there is some research to suggest they are not 100% the same. you and your brother share very similar dna because you have the same parents, and you look the same. i'll bet you resemble one or both of your parents, and likely a grandparent or two as well.