DNA and Molecular Biology Overview

DNA and RNA are nucleic acids
Nucleotides are the structural units of nucleic acids
Nucleotides are composed of a nitrogenous base, a pentose sugar, and a phosphate group
Nucleosides are composed of a nitrogenous base and a pentose sugar
Purines include adenine and guanine
Pyrimidines include cytosine, uracil, and thymine
Ribose is the pentose sugar in RNA
Deoxyribose is the pentose sugar in DNA
Major pyrimidines include uracil, thymine, and cytosine
Minor pyrimidines include dihydro uracil and methyl cytosine (hydroxy methyl cytosine)
Major purines include adenine and guanine
Oxy purines include hypoxanthine and xanthine, Uric acid is the end product of purine catabolism
Methylated purines include caffeine, theophylline, theobromine
Nucleotides are named based on the nitrogenous base
Nucleosides are named based on their nitrogenous base
e.g., Adenylic acid (AMP) is the monophosphate form of Adenosine
ATP is a source of energy in the body
High-energy bonds between phosphate groups
Signaling second messenger (hormone 2nd messenger)
cAMP (cyclic AMP) and cGMP (cyclic GMP)
cAMP can activate protein Kinase A causing phosphorylation
cAMP acts in signal transduction
Methylated derivatives are important for biosynthesis
SAM (S-Adenosyl Methionine) is the most important methyl donor
PAPS (phosphoadenosine 5'-phosphosulfate) is a sulfate donor
Other forms of RNA: snRNA, miRNA, and siRNA

Nucleosides are formed by attaching a nitrogenous base to a pentose sugar via a glycosidic bond.
This attachment is at position 1' on the pentose sugar.
Position 9' for purine and 1' for pyrimidine
Nucleotides are formed by attaching one or more phosphate groups to the 5' carbon of the pentose sugar in a nucleoside.
The attachment is by a phosphate ester bond.
Carbon atoms of the pentose sugar are numbered as 1', 2', 3', 4', and 5'.

Nucleotides and nucleosides are the building blocks of DNA and RNA
They play important roles in many biochemical functions, including energy transduction and signaling pathways.

Nucleic acids are polymers of nucleotides, which are composed of a nitrogenous base, pentose sugar, and phosphate group.
There are two main types: DNA and RNA.
DNA typically has a double helix structure, whereas RNA is usually single-stranded
Primary structure: Sequence of nucleotides along a polynucleotide strand
Secondary structure: Specific three-dimensional arrangement of a polynucleotide strand. For example, DNA forming a double helix
Tertiary structure is the overall 3D arrangement of a nucleic acid strand or its double helix
DNA structure has a double helix.
Stability is maintained by hydrogen bonds between nitrogenous bases, Van der Waals forces, and hydrophobic interactions
DNA is primarily linear but also exists as supercoiled circular forms.
Mitochondria, and some types of bacteria contain circular DNA

Various non-coding RNAs play important roles in gene expression regulation and other cellular processes.

mtDNA is a small, circular, double-stranded DNA molecule
It is inherited maternally
mtDNA codes for some proteins and RNA molecules crucial for energy production in mitochondria.

Genes are sequences of DNA that code for proteins.
Alleles are different forms of a gene.
The genome is the complete set of genetic material in an organism.
Exons are the coding regions of a gene, while introns are the non-coding regions.
Phenotype is the observable characteristics of an organism.
Genotype is the genetic makeup of an organism.