This is due to the similar electronic configuration (more importantly the number of valence electrons). Among the two groups given here, choice (b) Mg, Sr and Ba are alkaline earth elements (part of group IIA) in the periodic table. Other elements of this group are Be, Ca and Ra. All these elements form the alkaline earth metal group of the periodic table. All these elements have 2 valence electrons, which they can give up to attain a +2 charge as cations. They have certain common properties, including shiny and silver-white appearance.
The backbone of the DNA strand is made from alternating phosphate and sugar residues. The sugar in DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings.he backbone of the DNA strand is made from alternating phosphate and sugar residues. The sugar in DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings.
DNA ligase is an enzyme which seals gaps in the sugar-phosphate backbone of DNA molecules. This is necessary in the replication of DNA as the lagging strand is synthesised i â¦ n short fragments by DNA polymerase. The gaps between the fragments are then sealed by DNA ligase.