heredity

             always linked.
             to cytosine by three hydrogen bonds. This is known as base pairing.
             (Miller, 143).
             The DNA of an organism provides two main functions. The first.
             function is to.
             provide for protein synthesis, allowing growth and development of the.
             organism. The.
             second function is to give all of it's descendants it's own.
             protein-synthesizing information.
             by replicating itself and providing each offspring with a copy. The.
             information within the.
             bases of DNA is called the genetic code. This specifies the sequence of.
             amino acids in a.
             protein. (Grolier Encyclopedia, 1992) DNA does not act directly in the.
             process of.
             protein synthesis because it does not leave the nucleus, so a special.
             ribonucleic acid is used.
             as a messenger (mRNA). The mRNA carries the genetic information from the.
             DNA in the.
             nucleus out to the ribosomes in the cytoplasm during transcription.
             (Miller, 76).
             This leads to the topic of replication. When DNA replicates, the.
             two strands of.
             the double helix separate from one another. While the strands separate,.
             each nitrogenous.
             base on each strand attracts it's own complement, which as mentioned.
             earlier, attaches.
             with hydrogen bonds. As the bases are bonded an enzyme called DNA.
             polymerase.
             combines the phosphate of one nucleotide to the deoxyribose of the.
             opposite nucleotide.
             This forms a new polynucleotide chain. The new DNA strand stays attached.
             to the old.
             one through the hydrogen bonds, and together they form a new DNA double.
             helix.
             molecule. (Heath, 119) (Miller, 144-145).
             As mentioned before, DNA molecules are involved in a process.
             called protein.
             synthesis. Without RNA, this process could not be completed. RNA is the.
             genetic.
             material of some viruses. RNA molecules are like DNA. They have a long.
             chain of.
             macromolecules made up of nucleotides. Each RNA nucleotide is also made.
             up of three.
             basic parts. There is a sugar called ribose, and at one end of the sugar.
             is the phosphate.
             group, and at the other end is one of several nitrogenous bases.