Associate Program Material
Answer the following in at least 100 words:
1. Describe the structure of DNA.
The three-dimensional structure of DNA – the double helix – arises from the chemical and structural feature of its two polynucleotide chains. Because these two chains are held together by hydrogen bonding between the bases on the different strands, all the bases are on the inside of the double helix, and the sugar-phosphate backbones are on the outside. In each case, a bulkier two ring base is paired with a single-ring base; A always pairs with T, and G with C. In this arrangement, each base pair is similar width, thus holding the sugar-phosphate backbones an equal distance apart along the DNA molecule. To maximize the efficiency of base-pair packing, the two sugar-phosphate backbones wind around each other to form a double ...view middle of the document...
This molecular chain of command is from DNA in the nucleus to RNA to protein synthesis in the cytoplasm. The two main stages are transcription, the transfer of genetic information from DNA into an RNA molecule, and translation, the transfer of the information from RNA into a protein.
3. Describe each stage of the flow of information starting with DNA and ending with a trait.
The flow of information from gene to protein is based on the triplet code. The genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as a series of three-base words called codons. Three-base codons in the DNA are transcribed into complementary three-base codons in the RNA, and then the RNA codons are translated into amino acids that form a polypeptide. For example: one DNA codon (three nucleotides) – one RNA codon (three nucleotides) – one amino acid. A genetic trait would be the red color seen in the flower petals. In the cytoplasm of the cell, a chemical reaction is taking place in which a colorless molecule is being converted into a red pigment molecule. As with all chemical reactions within cells, this conversion reaction is catalyzed by an enzyme catalyst. Without this enzyme catalyst, the reaction would proceed so slowly that little or no pigment would be produced. The enzyme catalyst makes the chemical reaction proceed at life speed. When the enzyme is present in the cell it can produce a lot of pigment and pigment granules. The flower petals turn red as these granules accumulate in the cells, creating a genetic trait.
(Alberts, Johnson, Lewis, Raff, Roberts, & Walter, (2002). National Center for Biotechnology Information, U. S. National Library of Medicine. Bethesda, MD.www.ncbi.nlm.nih.gov/2002)
(Simon, Reece, & Dickey (2010). Campbell essential biology with physiology (3rd ed). San Francisco, CA: Pearson Benjamin Cummings)
(Professor John Blamire, (2005). Science at a Distance. www.brookly.cuny.edu)