You must have the right sequence of amino acids in order for the protein to function correctly; (analogy: if you need a protein to write a check, you can't do it with the sequence of a screwdriver.)

1. Characteristics
   -
1. Genetic information molecule of life
   The UNIVERSAL information molecule of life. (Whether or not viruses are living things is debatable, and some have RNA and no DNA).
2. Common to all living things
   ALL living things.
3. Controls manufacture of proteins
   (Review the 4 points at the beginning of this lecture.)
4. Information storage molecule
   Genetic information is stored in DNA.
5. Self-replicating, double helix
   DNA is a double molecule. (If you can envision DNA as a twisted ladder, each molecule of DNA is a side, and the rungs between them are the hydrogen bonds between the nitrogen bases of each molecule.)
2. Chemical make-up (basic building blocks: nucleotides)
   9.1 Nucleotide
   
1. Five-carbon sugar
   Deoxyribose (DNA = Deoxyribose Nucleic Acid)
2. Phosphate group
   
3. Nitrogen base (four possibilities:)
   Adenine, Guanine, Thymine, Cytosine. Nitrogen bases match up consistently: Adenine always matches with Thymine (2 hydrogen bonds between them); Guanine always matches up with Cytosine (3 hydrogen bonds between them).
3. Functions of DNA
   Important stuff.
1. Information storage
   All the genetic information needed to build a working organism (you for example) is stored in DNA.
2. Information transmission
   DNA transmits its stored, genetic information by way of protein synthesis.
3. Control of protein synthesis
   DNA, ULTIMATELY, dictates the synthesis of proteins (because it controls transcription (the synthesis of mRNA, which DIRECTLY controls protein synthesis).
4. Self-replication
   9.2 DNA Replication
   DNA has the capacity to copy itself: enzymes pull apart the two molecules (sides/halves) of the DNA strand; then by matching the sequence of nitrogen bases (A-T, C-G), each half (side) is able to construct a new half of DNA: a replicate of its complementary half (side). When completed we have two identical strands of DNA. DNA replication always happens before cell division: (when one of Gerald's cells divides, the first thing that happens is that all of the cell's DNA will replicate itself: the 46 chromosomes will replicate into 92 (each chromosome is a single, double-helical DNA strand), and then be equally divided between cells, each with a duplicate copy of the 46 chromosomes). (More on this when we discuss Mitosis.)

Summary: by matching consistently the nitrogen bases of the two 'old' halves of the DNA with a new sequence of nitrogen bases to reform the 'missing' half, we end up with two identical molecules of DNA. (Where do the extra/new nucleotides come from? They are available in the cell (in the nucleus, where transcription occurs).

What does DNA have to do with asking a beautiful girl (Phospho Rindy) to homecoming? (Maybe a lot.)

RNA
9.3 Nucleic Acid

1. Characteristics
   Another type of nucleic acid.
1. Involvement in protein synthesis
   RNA controls protein synthesis DIRECTLY.
2. Transcribed from DNA
   RNA comes from (is transcribed from) a DNA blueprint: transcription.
3. Single helix
   A single nucleic acid molecule.
2. Chemical make-up (basic building blocks: nucleotides)
   Much in common with DNA.
1. Five-carbon sugar
   Ribose
2. Phosphate group
   
3. Nitrogen base (four possibilities:)
   Adenine, Guanine. Cytosine, URACIL.
3. Types and functions of RNA
   (Structurally, they are pretty much the same, but functionally they vary.)
1. Messenger RNA (mRNA)
   Provides the working blueprint for properly assembling the sequence of amino acids in a protein. (Can you recite the four points made at the beginning of this lecture?) For every kind of protein (your) cells can make, there is a different mRNA. (So if a cell can make 5000 different proteins, it can produce 5000 different mRNAs.)
2. Transfer RNA (tRNA)
   Several functions: 1) tRNA picks up an amino acid (from cell reservoir), 2) transfers the amino acid to the site of protein synthesis (ribosome), 3) reads the mRNA working blueprint and properly positions its amino acid. Each tRNA will pick only one kind of amino acid, so we need a minimum of 20 tRNAs: one for each kind of amino acid. (Do vegetarians have trouble getting the right quantities of all the 20 amino acids? Much of the plant world is deficient in some of the amino acids, so there is a risk, but a vegetarian who is diet-conscientious (about getting adequate proteins) is OK.
3. Ribosomal RNA (rRNA)
   Remember Dr. Cates talking about the nucleolus? Ribosomal subunits are assembled there. The rRNA is a structural part of the ribosome that functions to assist the tRNA and mRNA in precisely positioning each amino acid. (If the amino acid sequence is not precisely accurate, the protein will have the wrong structure and, therefore, will not function properly. (Example: if one amino acid of a particular protein in our blood is out of sequence it causes serious, life-threatening problems with our hemoglobin.)

1. DNA
   
1. Sugar: deoxyribose
   
2. Nitrogen bases:
   (Adenine, Guanine, Cytosine, *Thymine)
   
3. Double-stranded
   
2. RNA
   
1. Sugar: ribose
   
2. Nitrogen bases:
   (Adenine, Guanine, Cytosine, *Uracil)
   
3. Single-stranded
   

1. A two step process:
   
1. Transcription:
   DNA ==> RNA
   9.4 Transcription
   The first step in protein synthesis--involves taking information in the DNA form and using it to organize RNA molecules. Overview statement: Information from a segment of DNA is used to organize an RNA molecule. Transcription is accomplished by temporarily matching DNA and RNA nitrogen bases. Literally, the sequence of DNA nitrogen bases serves as a pattern for positioning RNA nucleotides (thus assembling the RNA). (All types of RNA are assembled in this manner (by transcription). The type of RNA is differentiated by the segment of DNA from which it was transcribed.) When transcription is completed, the two halves of the DNA come back together. (Note in the figure 9.4 that the RNA polymerase is an enzyme involved in this process.)
1. Takes place within the nucleus of eukaryotic organisms
   (The nuclear DNA doesn't leave the nucleus. Where else do we find DNA (non-nuclear)in eukaryotic cells? Mitochondria, chloroplasts (prokarytic type DNA: remember Endosymbiotic theory?)
2. Translation:
   mRNA + tRNA + amino acids ----> protein
   9.5 Translation
   The second stage of protein synthesis--involves the mRNA receving the tRNAs with their specific amino acids, which are bonded to form specific proteins (polypeptide chains). These proteins are the end product of translation. Translation is accomplished by temporarily (using hydrogen bonds) matching the anticodon (3 sequential nitrogen bases of the tRNA) with the codon (3 sequential nitrogen bases of the mRNA). A--U, C--G. This procedure allows for the proper positioning of each amino acid; thus, three nitrogen bases on the mRNA call for the positioning of a single amino acid. (How many amino acids/codon? (1). How many nitrogen bases/codon? (3). How many nucleotides/amino acid? (3). Be able to calculate using larger numbers (example): in using 93 anticodons, how many amino acids have been positioned? (93); if a segment of mRNA transcribes for a protein containing 3000 amino acids, how many nucleotides are in that segment of mRNA? (9000) How many anticodons were used? (3000).

The same sequence of nitrogen bases in the codon will always code for the same amino acid, but not visa versa: various codon sequences may code for the same amino acid. So, though there are only 20 amino acids, there can be (and are) more than 20 codon sequences. Example: suppose the codon sequence AUA codes for amino acid#5. It will never code for another amino acid. Another codon sequence, say UUU, may also code for amino acid#5, and, likewise, will never code for anything else.

1. Takes place at the ribosome
   The ribosomal subunits are used to match up the mRNA's codon with the tRNA's anticodon, enabling protein synthesis to take place.
2. Factors affecting protein synthesis
   
1. Environmental factors
   Much of homeostasis involves maintaining suitable environment for metabolism, (which includes protein syynthesis). Two environmental factors we must deal with: temperature and pH: each must be maintained within certain limits or disaster. (temperature: around body temperature (around 98.6); pH: neutral (around 7)).
2. Materials and energy
   We must have a supply of amino acids: plants can manufacture all 20 amino acids from scratch by taking the photosynthetic products, rearrange a few molecules. You and I get our amino acids from what we eat.
   Also, we need sufficient ATP (energy).

Protein Synthesis: Amino Acid Rock?(If you have theRealAudio Player.)