Lecture Outline - Chapter 20

20.1 DNA and RNA Structure and Function (p. 416, Fig. 20.2)
	1.	DNA Structure and Replication (p. 417, Figs. 20.3, 20.4)
		a.	Nucleotides are composed of a phosphate, a sugar, and a base. DNA has the sugar deoxyribose and four different bases: adenine (A), thymine (T), guanine (G), and cytosine (C). DNA is cell's genetic material.
		b.	There is complementary base pairing within DNA. A always pairs with T, and G with C.
		c.	The sugar-phosphate backbone forms the uprights of the DNA double helix, with the base pairs comprising the rungs of the ladderlike shape.
		d.	DNA Can Be Replicated (p. 418, Fig. 20.5)
			i.	DNA replication occurs during chromosome duplication. 
			ii.	First, hydrogen bonds between bases break, and enzymes "unzip" the molecule.
			iii.	New nucleotides move into complementary positions.
			iv.	New nucleotides are joined by DNA polymerase.
			v.	The new DNA molecules are complete, with each parent strand serving as a template for a new strand. Thus, the duplication is semiconservative.
	2.	Structure and Function of RNA (p. 419, Fig. 20.6, Table 20.1)
		a.	RNA is a single strand of nucleotides containing the sugar ribose. The base uracil (U) replaces thymine in RNA. RNA is a helper molecule in protein synthesis.
		b.	Ribosomal RNA (p. 419)
			Ribosomal RNA (rRNA) is formed off a DNA template in the nucleolus. It then leaves the nucleus to join with proteins to form the subunits of ribosomes. 
		c.	Messenger RNA (p. 419)
			Messenger RNA (mRNA) forms off a DNA template in the nucleus and carries genetic information out to the cytoplasm for protein synthesis.
		d.	Transfer RNA (p. 419)
			Transfer RNA (tRNA) forms off a DNA template in the nucleus and transfers amino acids to the ribosomes, where protein is synthesized.
20.2 DNA Specifies Proteins (p. 420)
	1.	Structure and Function of Proteins (p. 420, Fig. 20.7)
		a.	Proteins are composed of building blocks called amino acids. Twenty amino acids are found in cell proteins.
		b.	Proteins differ in the number and sequence of their amino acids, which also determine the protein's shape.
		c.	Some proteins serve structural functions, and others are enzymes.
	2.	DNA Code (p. 420, Table 20.2)
		a.	A gene is a sequence of DNA that codes for a protein.
		b.	DNA contains a triplet code.
		c.	The genetic code is universal--used by all organisms.
	3.	Transcription (p. 420, Fig. 20.8)
		a.	During transcription, DNA serves as a template for mRNA. RNA polymerase joins the nucleotides.
		b.	The triplet code of DNA translates to a codon of mRNA.
		c.	Processing mRNA (p. 421)
			DNA contains exons and introns. Before mRNA leaves the nucleus, the introns are excised so that only the exons are expressed.
	4.	Translation (p. 422)
		During translation, tRNA brings in the appropriate amino acid, matching up its complementary anticodon triplet of bases to the mRNA's triplet codon (Fig. 20.9).
	5.	Translation Requires Three Steps (p. 422, Figs. 20.10, 20.11)
		a.	During initiation, mRNA binds to the ribosome.
		b.	During elongation, the polypeptide is constructed, one amino acid at a time.
		c.	During termination, a stop-codon sequence is reached, and the ribosome falls away from the mRNA molecule.
	6.	Let's Review Protein Synthesis (p. 424, Fig. 20.12, Table 20.3)
		a.	DNA contains a triplet code for each amino acid.
		b.	During transcription, DNA serves as a template for mRNA.
		c.	Messenger RNA is processed before it leaves the nucleus, during which time its introns are removed.
		d.	Messenger RNA leaves the nucleus and becomes associated with a ribosome.
		e.	Transfer RNA molecules bring in amino acids, whose anticodons are complementary to the mRNA codons.
	7.	Control of Gene Expression (p. 425)
		a.	The cell can control gene expression in several ways.
		b.	Gene expression can be controlled in the nucleus during transcription (transcriptional control) or after transcription (posttranscriptional control) or in the cytoplasm in translational control at the ribosome or posttranslational control.
		c.	Activated Chromatin (p. 425, Fig. 20.13)
			For genes to function in cells, the chromosome must first decondense in the area to be transcribed.
		d.	Transcription Factors (p. 425)
			DNA-binding proteins, called transcription factors, regulate gene activity during cell specialization.
20.3 Biotechnology (p. 426)
	1.	Biotechnology uses genetic engineering to achieve the desired end. Genetic engineering allows the insertion of a foreign gene into new cells, which are then able to produce a different product.
	2.	Cloning of a Gene (p. 426)
		a.	Choosing a Vector (p. 426, Fig. 20.14)
			Recombinant DNA contains DNA from two or more different sources. A technician selects a vector (plasmid) that will provide a means of getting a gene into a host cell. When many copies of the foreign gene are obtained, the gene is said to be cloned. Viruses are also used as vectors.
		b.	Making Recombinant DNA (p. 427)
			Making recombinant DNA requires the use of a restriction enzyme that cleaves the plasmid DNA at a specific sequence, leaving "sticky" ends, and DNA ligase that seals openings in the DNA. 
		c.	Getting the Product (p. 427, Tables 20.4, 20.5)
			Reverse transcriptase is useful for making a DNA copy of mature mRNA--one without introns.
	3.	Replicating Small DNA Fragments (p. 428, Fig. 20.15)
		a.	The polymerase chain reaction can produce millions of copies of a single gene or piece of DNA. Primers on either side of the target DNA get the chain reaction going.
		b.	Analyzing DNA Segments (p. 428)
			i.	Automated DNA sequencers use computers to sequence genes rapidly.
			ii.	A DNA probe is a strand of radioactive DNA made by a synthesizer. The DNA probe binds to a specific area on DNA and may be used to detect viral infections and diagnose genetic disorders and cancer.
	4.	Making Transgenic Organisms (p. 429)
		a.	Transgenic organisms are natural organisms that have a foreign gene inserted into them.
		b.	Transgenic Bacteria Perform Services (p. 429, Fig. 20.16)
			i.	Transgenic bacteria are used to transfer genes for insect toxins to plants to help plants resist insects without use of pesticides.
			ii.	Transgenic bacteria can degrade normally nonbiodegradable substances.
			iii.	Transgenic bacteria can be made to produce chemicals, like phenylalanine.
			iv.	Transgenic bacteria are used in mineral processing to extract copper, uranium, and gold.
		c.	Transgenic Plants Are Here (p. 430, Fig. 20.17)
			Plants have been genetically engineered to resist pests, and others will one day be temperature-, drought-, or salt-tolerant; will require less fertilizer; will be able to be shipped without damage; will be more nutrious; and will produce needed drugs and medicines.
		d.	Transgenic Animals Are Here (p. 430, Fig. 20.18)
			Bovine growth hormone has been inserted into many different animals, resulting in the production of larger stock animals. Gene pharming, the use of transgenic farm animals to produce pharmaceuticals, may one day produce substances that will kill many infections and treat other disorders.
		e.	Ecological Concerns (p. 431)
			Tools are now available to detect, measure, and stop cell activity in the natural environment. 
			ECOLOGY FOCUS: Biotechnology: Friend or Foe? (p. 431, Fig. 20A)
			This focus considers the pros and cons of genetic engineering.
	5.	Gene Therapy Is a Reality (p. 432)
		a.	Some Methods Are Ex Vivo (p. 432, Fig. 20.19)
			Some methods of gene therapy are ex vivo--cells are removed, treated, and returned to the body.
		b.	Some Methods Are In Vivo (p. 432)
			In vivo methods are performed inside the patient's body. For example, the healthy cystic fibrosis gene can be successfully inhaled.
		6.	Mapping Human Chromosomes (p. 433, Fig. 20.20)
			The Human Genome Project involves many laboratories throughout the world that are mapping the human genome.