The Structure of DNA

Basic Structure DNA is often compared to a twisted ladder. The rails of the ladder consist of alternating deoxyribose and phosphate. The rungs/steps of the ladder are paired nitrogenous bases.

A closer look at the nucleotides A nucleotide is the building block of the DNA structure. It consists of a five carbon sugar and a phosphate group, which make up the backbone of DNA. It also consists of a nitrogenous base.

Let’s examine the backbone The backbone consists of a sugar and a phosphate group. The two backbone strands are said to be ANTIPARALLEL. One side the backbone runs from 5’ to 3’. On the other strand, the backbone runs from 3’ to 5’. The numbers 5’ and 3’ are in reference to the bonding carbon atoms in deoxyribose.

There are four types of nitrogenous bases in a DNA molecule General Information The four types of nitrogenous bases in DNA are THYMINE, CYTOSINE, ADENINE, and GUANINE. Thymine and cytosine are known as PYRIMIDINES because of their single ring structure. Adenine and guanine are known as PURINES because of their double ring structure.

Remember Chargaff’s Rule In a DNA molecule the bases bond together to create stability in the molecule Remember Chargaff’s Rule How does base pairing work? Adenine= Thymine Cytosine= Guanine Purines are bonded to pyrimidines Adenine bonds to Thymine There are two hydrogen bonds present that hold the bases together Cytosine bonds to Guanine There are three hydrogen bonds present that hold the bases together

Both DNA and RNA are hereditary, genetic material Both DNA and RNA are hereditary, genetic material. They both are nucleic acids. How are they different? RNA DNA RNA is typically single stranded. RNA contains the bases: Cytosine, Guanine, Adenine and Uracil Contains the sugar ribose DNA is typically double stranded DNA contains the bases: Cytosine, Guanine, Adenine, and Thymine Contains the sugar Deoxyribose