WATSON AND CRICK
Base pairs---Attached to each sugar ring is a nucleotide base, one of the four bases Adenine, Guanine, Cytosine, and Thymine. The hydrogen bonding between complementary bases holds the two strands of DNA together. Hydrogen bonds are not chemical bonds
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Karyotype-the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
Replication depends on the pairing of bases between the two strands of DNA. The A base can only bind to a T, and a C can only bind to a G. Replication begins at a location on the double helix known as “oriC” to which certain initiator proteins bind and trigger unwinding. Enzymes known as helicases unwind the double helix by breaking the hydrogen bonds between complementary base pairs, while other proteins keep the single strands from rejoining. With the primer as the starting point for the leading strand, a new DNA strand grows one base at a time. The existing strand is a template for the new strand. For example, if the next base on the existing strand is an A, the new strand receives a T. The enzyme DNA polymerase controls elongation, which can occur only in the leading direction. The lagging strand unwinds in small sections that DNA polymerase replicates in the leading direction. After elongation is complete, two new double helices have replaced the original helix. During termination, the last primer sequence must be removed from the end of the lagging strand.