Once you are done with this lesson you should be able to: 1  Identify the Abbasids. 2  Describe the roles of the caliphs and the viziers. 3  Explain how the caliphs' focus on trade led to the Golden Age of Islam. 4  Summarize the fall of the Abbasids.
Alleles are forms of the same gene with small differences in their sequence of DNA bases. These small differences contribute to each personâs unique physical features. Genes are made up of DNA.Each chromosome contains many genes. A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.lleles are forms of the same gene with small differences in their sequence of DNA bases. These small differences contribute to each personâs unique physical features. Genes are made up of DNA.
1 One gene makes one protein. 2  A gene is made of DNA. 3  Bacteria and viruses have DNA too. 4  The DNA molecule is shaped like a twisted ladder. 5  A half DNA ladder is a template for copying the whole.  RNA is an intermediary between DNA and protein.