These bases always bond in a certain way. The bases are known by their coded letters A, G, T, C. The pyrimidines are thymine and cytosine. Two of the bases are purines - adenine and guanine. The rungs of the ladder are pairs of 4 types of nitrogen bases. The sugar is deoxyribose.Ĭolor all the phosphates pink (one is labeled with a 'p'). The sides of the ladder are made of alternating sugar and phosphate molecules. The structure is a double helix, which is like a twisted ladder. In 1953, James Watson and Francis Crick established the structure of DNA. We now know that DNA is also found in organelles, the mitochondria and chloroplasts, though it is the DNA in the nucleus that actually controls the cell's workings. DNA is called a nucleic acid because it was first found in the nucleus. Meanwhile, DNA is the chemical that genes and chromosomes are made of. Hence you hear it commonly referred to as the gene for baldness or the gene for blue eyes. A gene is a segment of DNA that codes for a particular protein, which in turn codes for a trait. These proteins in turn, form the structural units of cells and control all chemical processes within the cell.Ĭhromosomes are composed of genes. In simple terms, DNA controls the production of proteins within the cell. How does it do this? Chromosomes, found in the nucleus, are microscopic, threadlike strands composed of the chemical DNA (short for deoxyribonucleic acid). It is often called the 'control center' because it controls all the activities of the cell including cell reproduction, and heredity. The nucleus is a small spherical, dense body in a cell.

Genetics a twisted tale worksheet