DNA, RNA, and Proteins
Mitosis and Cell Division

         I. Introduction
            A. DNA structure discovered in 1953 by J. Watson and F. Crick
            B. How does DNA work?  How are genes passed on to new plant (and animal) cells?

        II. Definitions to know
            A. Genetics = the study of heredity and hereditary variation
            B. Heredity = passing on biological traits from one generation to the next generation.
            C. Gene = basic unit of heredity; sequence of DNA that codes for single or several proteins.
            D. Chromosome = a very long DNA molecule wrapped around proteins called histones, causing the DNA to coil (or condense).
                (Human cell = 46 chromosomes or 23 sets).
            E. Genotype = genetic make-up.
            F. Phenotype = appearance (genes expressed).

        III. Heredity and the environment
                Phenotype = genotype + environment

        IV. Why genes are important?
            A. Chromosomes are made of genes.  Genes are made of DNA (deoxyribonucleic acid).  DNA is found in the nucleus.
            B. DNA Structure (review)
                    1. DNA is a double helix (it is two stranded or double stranded).  Each strand is a complement of the other.
                    2. DNA is a nucleic acid = polymer of nucleotides (the monomers).
                        a) DNA Nucleotide = a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogen base: Adenine (A), Guanine (G),
                            Cytosine (C), and Thymine (T).
                        b) Base pairing: A pairs only with T and G pairs only with C.
            C. DNA function (review)
                    1. Contains coded information that programs all cell activity.
                    2. Genes are the blueprints for the production of proteins.
                    3. Contains directions to make more of itself (replication).

         V. DNA replication = DNA synthesis on a DNA template in the nucleus
            A. DNA has the ability to make exact copies of itself
            B. Semiconservative replication.

        VI. How genes work
            A. Universal rule: DNA--->mRNA---->PROTEINS
            B. mRNA is a single stranded nucleic acid
                    1. Three RNA types: mRNA, tRNA, rRNA
                    2. mRNA Nucleotide = a 5-carbon sugar (ribose); a phosphate group; and a nitrogen base: (A), (G),  (C), and Uracil (U).
            C. Transcription = synthesis of mRNA using DNA as a template in the nucleus
            D. Translation = synthesis of a protein in the cytosol from amino acids according to the sequence of mRNA nucleotides.
                    1. Genetic code passed on to mRNA from DNA is represented by codons (triplet combinations of mRNA nucleotides).
                    2. Each tRNA also has a triplet combination of nucleotides, but in tRNA it is called an anticodon.
                    3. Genetic code: every three nucleotides on mRNA codes for a particular amino acid – reads 3 at a time.
 
                            Example:

                                       mRNA             U – G – G – U – U – U – G – G – C – U – C – A  
                                                                    codon          codon         codon        codon
                                       amino acids         Trp------------Phe -----------Gly----------Ser

                    4. The code is universal: all living things have the same code!

        VII. Cell cycle
            A. Cell division = reproduction of cells. For reproduction (unicellular organisms); growth, development, repair, cell replacement.
            B. Cell cycle: the life of a cell, from its origin in the division of a parent cell until its own division into two cells.
                    1. interphase: G1, S, G2
                    2. mitosis: division of nucleus
                    3. cytokinesis: division of cytoplasm
            C. Mitosis steps: prophase, metaphase, anaphase, and telophase
                    1. Key points: mitosis occurs in somatic cells = non sex cells
                    2. 2n ---> 2n
                    3. Exact duplication of DNA