Chromosomes and DNA Replication Chapter 12.2 Chromosomes and DNA Replication

DNA and Chromosomes Prokaryotic cells have 1 single circular chromosome. Eukaryotic DNA is in the cell nucleus and usually linear (straight line) and more than 1. Humans have 46 chromosomes, Fruit flies have 8, and a giant sequoia tress has 22.

DNA Length DNA molecules are very long. For example an E. coli DNA is made of 4,639,221 base pairs.

Chromosome Structure A human cell has almost 1000 times as many base pairs as E. coli. Eukaryotic chromosomes are made of DNA and proteins and make up chromatin. Chromatin is DNA tightly wound around proteins called histones. Together DNA and a histone form a beadlike structure called a nucleosome. These nucleosomes allow DNA to fold up.

DNA Replication Because of base pairing (A pairs with T and G with C) this allows replication. If we separate the 2 strands in the double helix we will be able to construct new strands. Watch the video: https://www.youtube.com/watch?v=27TxKoFU2Nw

Duplicating DNA Replication is the copying of DNA. During replication the DNA molecule separates into 2 strands and then produces 2 new complementary strands following the rules of base pairing. So if we have the strand TACGTT it will produce the strand ATGCAA. (we will go over this in class!)

How Replication Occurs Enzymes are very important in DNA replication. Some enzymes unzip the DNA molecules (unwind the 2 strands and separate them). This is important for each old strand to serve as a template to make a 2 new strands. DNA polymerase is the enzyme that aids in DNA replication.