分子生物学(双语)1 Genes Are DNA

FIGURE 07: Eukaryotic cells can acquire a new phenotype as the result of transfection
Basic DNA Structure
• Nucleotide – phosphate, sugar, base • Bases – pyrimidines and purines • Phosphodiester bonds – phosphate/sugar
FIGURE 20: Nucleic acids all replicate by synthesis of complementary strands
FIGURE 21: The amount of nucleic acid in the genome varies over an enormous range
– proofreading – mutations
FIGURE 15: Replication of DNA is semiconservative
FIGURE 16: The replication fork
FIGURE 17: An endonuclease cleaves a bond within a nucleic acid
FIGURE 13: The two strands of DNA form a double helix
© Photodisc
DNA Replication Basics
• Origins of replication • Semi-conservative • Denaturation, annealing, extension • DNA Polymerases
FIGURE 03: Griffith experiment
FIGURE 04: The DNA of S-type bacteria can transform R-type bacteria into the same S-type
FIGURE 06: The genetic material of phage T2 is DNA
backbone • 5’ to 3’ direction, antiparallel double helix • Base pairing • Minor versus major groove in B-DNA • 3.4 nm and 10.4 base pairs per turn • Alternative DNA structures
– Depends on complementarity
• Intermolecular or intramolecular • Hybridization is the key to many methods
FIGURE 23: Denatured single strands of DNA renature to give the duplex form
FIGURE 22: Base pairing
Hybridization
• Nucleic acids hybridize by base pairing • Denaturation is ds to ss
– Tm depends on sequence
• Renaturation is ds to ss
分子生物学（双语）1 Genes Are DNA
Figure CO: X chromosome in blue
© Science VU/DOE/Visuals Unlimited
FIGURE SO: Part I: Genes and Chromosomes
Photo courtesy of S. V. Flores, A. Mena, and B. F. McAllister. Used with permission of Bryant McAllister, Department of Biology, University of Iowa.
DNA as the Genetic Material
• Pneumococcus pathogenicity tranferred to normal strain by transformation
• T2 bacteriophage genetic material is DNA • Transfection of eukaryotic cells with TK+
FIGURE 19: The central dogma
Control of Gene Expression
• Processes affected by control • Complexity from control • Regulatory elements
cis-acting trans-acting
FIGURE 08: A polynucleotide chain
FIGURE 12: Flat base pairs lie perpendicular to the sugar-phosphate backbone
FIGURE 14: Base pairing provides the mechanism for replicating DNA
FIGURE 18: An exonuclease removes bases one at a time
Gene Expression
• Transcription
– Reverse transcription
• RNA processing • Translation • Post-translational modifications
© Mopic/ShutterStock, Inc.
FIGURE CO: Genes are DNA
FIGURE 01: A brief history of genetics
FIGURE 02: A gene codes for an RNA, which may code for protein