Chromosome Structure and DNA Replication 12-2 Chromosome Structure and DNA Replication

Chromosomes Prokaryotic cells Eukaryotic cells One single chromosome Shape? Eukaryotic cells Typically have ~1000 times the amount of DNA as prokaryotes Chromosome number varies between species Humans are 46, potato is 48 (4 sets of 12)

DNA length Very long Requires condensing in order to fit in cells DNA in E. Coli (bacteria) is over 1 million bases long, over 1 mm in length Human DNA is roughly 3 billion bases long, length is over 1 meter long Requires condensing in order to fit in cells Forms chromatin when tightly coiled around histone proteins Condenses into chromosomes during prophase

DNA Replication Each strand of DNA can be used to create a new one Replication forks: areas where separation of DNA strands and replication of new strands begins Essential for cell division to occur

DNA Replication Double helix separates, then each strand has a new complimentary strand created by DNA polymerase A to T and G to C DNA helicase: “unzips” the DNA Essential step for DNA polymerase to bind to DNA DNA polymerase Brings the new nucleotides together Responsible for proofreading the new DNA strands