BACKGROUND
      Naturally occurring mutations have created new genetic combinations since the origin of life. For
centuries, humans have developed and used selective crossbreeding to improve organisms used for
food, clothing, transportation, etc. Since the early 1970s, genetic engineers have developed molecular techniques to alter the genetic make-up of organisms. All three of these mechanisms involve changing
the genetic make-up of organisms. How do these changes in an organism's genetic make-up (genotype)
affect the trait that is expressed (phenotype)?
      Proteins provide the structural and functional basis of life. They play a part in every conceivable life
function:
      A structural protein called collagen helps make up cartilage and tendons. Another protein (keratin)
           is found in our hair and fingernails.
      Hemoglobin is a transport protein that carries oxygen through the bodv.
      Plant hormones such as auxins and gibberellins are proteins that enhance or regulate biochemical                messages. Insulin stimulates our blood to remove sugar.
      Proteins that catalyze chemical reactions in organisms are called enzymes. Amylase helps us to
           digest starches, and RNA polymerase assists with the transcription process that you will learn
           about in this lab.
      Proteins also perform many other functions, serving as antibodies, nutrient and waste transporters,
           nutrient storers, receptors and contractile proteins for muscles.

     Each link of a protein chain is a simple organic unit called an amino acid. There are 20 amino acids that
are used to form protein chains. The proteins we eat are broken down and then rearranged into the proteins
we need.
      DNA, a type of nucleic acid, is a long, double-stranded molecule made up of units called nucleotides.
One nucleotide consists of a deoxyribose sugar, a phosphate group and one nitrogenous base. The
sequence of nucleotides contains information necessary for making a chain of amino acids – a protein
chain. That sequence of nucleotides is called a gene. Sometimes several DNA sequences work together
to make a protein; a gene is not always one continuous stretch of DNA.
      Protein synthesis involves two basic processes, transcription and translation, that make use of
another nucleic acid, RNA. RNA, like DNA, is made up of a chain of nucleotides. In transcription,
enzymes transfer DNA's information to messenger RNA (mRNA) molecules. The mRNA molecules
then move out of the nucleus to the ribosomes, where protein synthesis occurs. The following table
shows how to read the genetic code in mRNA, and therefore can be used to determine the protein that
will result from that code.

     Translation is the process of decoding the transcribed DNA message contained in mRNA. A second
type of RNA, a cloverleaf shaped molecule called transfer RNA (tRNA) is involved. In the cytoplasm of
the cell, specific tRNAs attach to their particular amino acid. At the base of each tRNA molecule is a
sequence of three nucleotides (anticodon) that will recognize a complementary set of three nucleotides
on the mRNA molecule (codon). The tRNAs, bonded to their amino acids, move to the ribosome where
the mRNA is attached. The tRNA's and mRNA's bond together, as do the amino acids. The mRNA's and
tRNA's release from each other, and the sequence of amino acids that is left is what defines the protein.
      In this lab you will act out the steps of transcription and translation in protein synthesis. To accomplish
this task you will be given cards to line up to form:
           a) a row of DNA triplet codes
           b) a row of mRNA codons
           c) a variety of tRNA anticodons to arrange along the mRNA
           d) a variety of amino acids to attach to their corresponding tRNA

PROCEDURE
A. PREPARING THE NITROGEN BASE CARDS
1. Each lab group should obtain a handout with the DNA sequences and their complementary mRNA
    codes arranged as cards. Use scissors to roughly cut out all the cards for these two sequences. The
    cards are placed in groups of three letters because the nitrogenous bases of the genetic code function
    as triplet-base units. "The large letters on the cards refer to first letter of the nucleotide bases
    (A=adenine, C=cytosine, G=guanine, T=thymine, and U=uracil). The nucleotide base "thymine" found
    in DNA is replaced by the base "uracil" in all RNA molecules. The tRNA and amino acids cards should
    also be cut out, but will not be used until step #8.
2. Review DNA structure and the concept of complementary base-pairing. Recall that the “genetic
    code” of DNA is within the sequence of nitrogenous bases. Protein synthesis, just like DNA
    replication, does not begin until a stretch of DNA gets the signal to "unzip" and expose the
    nitrogenous bases.

B. TRANSCRIPTION
The DNA message is transcribed into mRNA by the enzyme RNA polymerase.
1. Assume that a strand of DNA has unzipped, exposing DNA's bases. In reality, one of the two
    strands is "active," while the other acts as a "dummy." You will be working with the active strand in
    this lab.
2. Position the DNA cards on your lab table. This are now represents the "nucleus" of a cell. Place the
    DNA card labeled "TAC” (the start sequence) on the left of the row of DNA cards. Next, the "ATC”
    (the stop sequence) card should be on the right of the row of DNA cards. All other DNA cards can
    be arranged in any order.
    NOTE -> Do NOT arrange your cards in the same order as the lab groups around you.
3. RNA polymerase catalyzes the pairing of DNA's exposed bases with complementary RNA bases.
    (Remember, only one of the two DNA strands is active.) Students should match the 3-letter
    sequence of the RNA cards (codons) with the 3-letter sequence of the DNA cards (triplets).
         RNA cytosine always pairs with DNA guanine.
         RNA uracil (Remember: “U" substitutes for "T") always pairs with DNA adenine.
         RNA adenine always pairs with DNA thymine.
         RNA guanine always pairs with DNA cytosine.
4. After you have matched up the DNA/RNA pairs fill in the appropriate table on the Data Sheet to
    show how you arranged these two sequences.
5. You have just simulated the process of transcription as it happens in protein synthesis. Notice you
    have made a very short (shorter than in real life) complementary section of RNA that almost reflects
    the exact opposite (complimentary) of the DNA code.

C. TRANSLATION
      The mRNA message is now translated into a chain of amino acids called a protein via enzymes and
tRNA. Notice that the tRNA cards are also arranged in groups of three letters. The three-base sequence of
tRNA is called an anticodon. Now the anticodon on each tRNA card will attract a specific one of the 20
amino acids needed by humans. In this lab you will only use seven of these 20 protein-building amino acids.
1. Now the tRNA and amino acid cards need to be aligned as they would in the "cytoplasm'' of the cell.
    First match the tRNA cards with their respective (and specific) amino acids. For example, the
    tRNA anticodon card "GGC" with attract the amino acid PROLINE (PRO on the card). NOTE ->
    Remember to convert the anticodon GGC to the codon CCG BEFORE using the Genetic Code table                provided above.
2. Now this tRNA/amino acid complex should be matched to the appropriate mRNA as if it were on the            ribosome. This process involves the movement of the ribosome down the mRNA strand. As the
    ribosome moves along the mRNA it reads the mRNA one codon at a time and attracts the appropriate
    tRNA anticodon. The result is a temporary union of mRNA + tRNA + amino acid.
3. Use the rules of complementary base-pairing:
         RNA cytosine always pairs with RNA guanine.
         RNA uracil always pairs with RNA adenine.
         RNA adenine always pairs with RNA uracil.
         RNA guanine always pairs with RNA cytosine.
4. As each tRNA anticodon finds its corresponding codon on the mRNA strand, the tRNAs detach from
    their amino acids. The amino acids remain at the ribosome and form a peptide bond with the amino
    acid brought by the previous tRNA. Two or more amino acids linked in this way are called
    polypeptides. Translation is complete when a sequence of mRNA information translates into a
    polypeptide. A protein is one or more polypeptide chains linked together.

D. PROTEIN SYNTHESIS QUIZ
      Upon completion of the lab above each lab group will complete the quiz attached to the Data Sheet.
The teacher will ask either student to point out the items with blank lines in front of them. Upon completion
of the quiz the questions associated with it should be completed along with the questions for the rest of the
lab.