2.1 DNA

2026-02-24 20:50

Status: #new

DNA is a biological polymer arranged in a double helic shape
Every monomer unit is called a nucleotide:
Pentose Sugar
- Structural backbone for the DNA
Phosphate groups
- Transfers ATP, provides structure and information
Sugar-phosphate Backbone
- Pentose Sugar and Phosphate groups come together to form a stable backbone
Nitrogenous Bases
- These are the variations of the nucleotide. They may differ. The different bases are:
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Thymine (T)
Nitrogenous Base Pairs
- Nitrogenous Bases always pair with one other base
  - A-T (2 Hydrogen Bonds)
  - G-C (3 Hydrogen Bonds)
- The order doesn't really matter as long as these are always bonded to each other

The DNA always comes in pairs. When undergoing mitosis, two identical DNA molecules are formed, half of them the new one and half of them the original.
DNA during interphase (OUTSIDE of Mitosis) are known as chromatin (de-condensed free-floating DNA), also known as a non-duplicated Chromosome
In preparation for mitosis, chromatin condense into duplicated chromosomes

Chromatid - One half of a replicated chromosome
Sister Chromatids - A pair of two identical Chromatids
Chromosome - A Condensed form of chromatin (when preparation for mitosis), consists of sister chromatids. Essentially a coiled molecule of DNA.
Duplicated Chromosome - A duplicated chromosome consisting of a pair of Sister Chromatids joined together at a centromere.
Centromere - An attachment point for spindle microtubules. It also holds together Sister Chromatids in a Duplicated Chromosome.

DNA (deoxyribonucleic acid) is copied into RNA (Ribonucleic Acid). Which are single nucleotide chains. This is done so that the DNA itself is not used.
The cell uses the RNA to make proteins
- Proteins make roughly 16% of the body yet they are used for:
- Enzymes
- Structure
- Signalling
- Transportation of nutrients
- Antibodies

References