Ch. 10

• Viruses that exclusively infect bacteria are called bacteriophages.
• Some bacterial viruses can be lysogenic (integrate into host genome) or lytic (replicate independently).
• Lysogeny is when a virus integrates its genetic material into the chromosomal DNA of the host cell.
• Bacteria have plasmids, which are small circular DNA molecules that replicate autonomously from the main chromosome.
• When induced, the phage enters the lytic cycle and replicates itself to produce many copies of the virus.
• The study of heredity at the molecular level is molecular biology.
• DNA and RNA are polymers of nucleotides
• A polynucleotide is a long chain of nucleotides
• The 4 nitrogenous bases are adenine, thymine, cytosine, and guanine
• Each nucleotide has a nitrogenous base, a sugar, and a phosphate group
• Nucleotides are joined together by covalent bonds between the sugar and the phosphate group
• A sugar-phosphate backbone is a pattern of sugar and phosphate joined by covalent bonds
• The sugar has 5 carbon atoms
• The phosphate group has a phosphorus atom at its center
• The sugar is called deoxyribose
• DNA is deoxyribonucleic acid
• DNA is located in the nuclei of cells and is the genetic material of the cell.
• The 4 nucleotides found in DNA differ only in the structure of their nitrogenous bases
• Thymine and cytosine are single-ring structures called pyrimidines
• There are 2 types of nitrogenous bases
• Adenine and guanine are larger, double-ring structures called purines
• RNA is ribonucleic acid
• RNA has a nitrogenous base called uracil instead of thymine
• DNA is a double-stranded helix
• Double helix is made up of 2 polynucleotide strands
• A purine must always be paired with a pyrimidine (*ex. A-T, C-G)
• A semiconservative model is when each new daughter molecule has one old strand of the original DNA molecules and one new strand
• Replication of a DNA molecule starts at sites called origins of replication
• The sugar-phosphate backbones run in opposite directions
• Each strand has a 3' (3 prime) end and a 5' (5 prime) end
• DNA polymerases are enzymes that link DNA nucleotides to a growing daughter strand
• DNA polymerases only add nucleotides to the 3' end of the strand
• A daughter DNA strand can only grow in a 5' to 3' direction
• Okazaki fragments are the DNA fragments that are synthesized during DNA replication.
• DNA ligase is an enzyme that links the fragments together into a single DNA strand
• DNA polymerases also remove nucleotides that have base-paired incorrectly during replication
• DNA replication ensures that all the somatic cells in a multicellular organism carry the same genetic information
• DNA helicases are enzymes that unzip and unwind the double-helix for replication
• Genes control the phenotypic traits through the expression of proteins.
• Proteins are the links between genotype and phenotype.