Inheritance - Chromosomes, genes and proteins

Chromosomes are thread-like structures made of DNA and proteins, found in the nucleus. They carry genetic information in the form of genes. In humans, the diploid number is $2n = 46$ and the haploid number is $n = 23$.

A gene is defined as a length of DNA that codes for a specific protein. Alleles are alternative forms of a gene that occupy the same locus on a chromosome.

DNA is a double helix consisting of two strands of nucleotides. Each nucleotide contains a phosphate group, a deoxyribose sugar, and a nitrogenous base: Adenine ($A$), Thymine ($T$), Cytosine ($C$), or Guanine ($G$).

DNA controls cell function by controlling the production of proteins (enzymes, antibodies, and receptors). The sequence of bases in a gene determines the sequence of amino acids used to build a specific protein.

Protein synthesis involves two stages: Transcription, where an $mRNA$ molecule is made from the DNA template in the nucleus, and Translation, where the ribosome reads the $mRNA$ codons to assemble amino acids into a polypeptide chain.

The genetic code is a triplet code. Each sequence of three bases, called a codon (e.g., $AUG$, $GCA$), specifies one amino acid.