eukaryotic cell DNA

• eukaryotic cells contain linear DNA molecules that exist as chromosomes - thread like structures made of one long molecule of DNA
• chromosomes are found in the nucleus
• DNA molecule is very long so has to be wound up so it can fit into the nucleus
• DNA is wound around proteins called histones
• histone proteins help support the DNA
• the DNA is coiled up very tightly to make a compact chromosome
• mitochondria and chloroplasts also have their own DNA which is circular and shorter than in the nucleus
• most DNA in eukaryotic cells doesn't code for polypeptides
• an intron is a section of a gene that doesn't code for an amino acid, even though the overall gene codes for a polypeptide
• the sections of a gene that does code for a polypeptide are called exons
• introns are removed during protein synthesis, so they don't affect the amino acid order