answers_learning_goals_ed_bms.pdf
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… chromosomes are made up of thousands of shorter segments of DNA, called genes. Each gene stores the directions for making protein fragments, whole proteins, or multiple specific proteins. What is the structure of DNA? DNA is a made from nucleotides: a combination of a phosphate group, a sugar molecule and a nitrogen group (also known as the nucleobases). In DNA, two strands of nucleotides are held together by hydrogen bonds between the nitrogenous bases and are intertwined, forming a so-called double helix. There are in total four nucleobases: adenine, cytosine, thymine and guanine. The combination of the nucleobases to form the connection between the strands of nucleotides, is set and always the same; A and T, C and G. A and G are purines which means they are made of two carbon nitrogen rings. C, T and U are pyrimidines which means they are made of a single carbon nitrogen ring. There are equal amounts of purines and pyrimidines found in the DNA. The bond between A and T is made of two hydrogen bonds (=non-covalent bonds), whereas the bond between G and C consists of three hydrogen bonds. The bond between A and T therefore is easier to break. DNA is antiparallel and complimentary. The side on which the phosphate group ‘extends’ is indicated by 3’, the side on which the …