Question

What is a residue? What is a phosphodiester bond? What is meant by the terms 5' end and 3' end? What does the term antiparallel mean? What is meant by the term base pairs? How do bases pair up? Draw two examples of base pairing. 

Answer 1

Ans 3) A residue is the material that remains after evaporation or distillation or any other sort of chemical events have taken place. It is basically defined as the undesirable byproduct of a particular type of chemical reaction. The phosphodiester bond is formed either between two DNA or two RNA molecules. It is defined as the bond between 3’ carbon of one sugar molecule and 5’-carbon of another.

The 5’ and 3’ ends are known as prime ends which refers to the number of carbon that is present in the backbone of the sugar. The 5’ carbon consists of a free phosphate group attached to it whereas the 3’ end of the carbon consists of a free OH group attached to it.

When we consider the term antiparallel in terms of DNA, it means that there are two strands that run side by side but in opposite direction. One strand of DNA runs in 5’ to 3’ direction where as the other one runs in 3’ to 5’ and hence both of them are anti-parallel

The base pair is when two complementary nitrogenous base pairs with each other and they are connected with help of hydrogen bonds. They are present in the ds DNA and they are possible by the complementary bonds formed between them.

The base pairs up in a way that thymine or uracil pairs with the adenine and guanine pairs up with the cytosine.

Two examples of base pairs are

1. A–G–T- A-C-C-C-
2. T- C–A -T-G-G-G-

2. A—U-C-G-C-A-C
3. U - T-G-C-G-U-G