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Chapter 16: Molecular Basis of Inheritance - Coggle Diagram
Chapter 16: Molecular Basis of Inheritance
16.3: Chromosome = DNA and Proteins
Chromatin = DNA and proteins packed together
Euchromatin = Less compact, more dispersed
Generally available for gene transcription
Heterochromatin
More packed
Histones bind to DNA + to each other
Forms nucleosomes (most basic unit of DNA packing)
Coiling + folding leads to tightly packed metaphase chromosomes
16.1: DNA = Genetic Material
The Search for Genetic Material
Evidence: Viral DNA can Program Cells
Bacteriophages = viruses that infect bacteria
Hershey-Case experiment =T2 protein tracked during infection of E. Coli
DNA discovered to enter bacteria
Viruses = DNA enclosed by protective layer (often just protein)
Evidence: DNA = Genetic Material
Erwin Chargaff studied DNA
Found DNA composition varied between species
Also noticed regularity in base number
Led to Chargaff's rules
DNA composition varies by species
A + T and C + G base ratios roughly equal for each species
Evidence: DNA can Transform Bacteria
Griffith's experiments
Mixed DNA of pathogenic bacteria with nonpathogenic
Discovered transformation
Transformation = change in geno/phenotype when cell acquires external DNA
Structural Model of DNA
Watson and Crick = focus on 3D structure
Determined the double helix shape
Watson constructed antiparallel model of DNA
16.2: Proteins and DNA Replication/Repair
Proofreading + Repairing DNA
DNA polymerases proofread DNA after pairing during synthesis
mismatch repair = fixing of pairing mistakes that evade proofreading
Nuclease = cuts out mismatched nucleotide
DNA polymerase + DNA ligase help fill gap
Nuclear excision repair = example of DNA repair system
Altered DNA Nucleotides: Evolutionary Significance
Permanent mistaken DNA sequence change due to replication = mutation
Mutations can change phenotype
Can be passed down generations
DNA Replication
Synthesizing New DNA Strand
Primer (RNA chain) synthesized by primase
DNA polymerases = catalyze DNA synthesis
Antiparallel Elongation
Each strand has directionality (5' or 3') + are antiparallel
Nucleotides only added to 3' end
Leading strand = DNA strand made during elongation
Lagging strand = synthesized discontinuously in segments
Segments = Okazaki fragments
DNA ligase joins Okazaki fragments
Getting Started
46 chromosomes
Origins of replication = where replication begins
Replication bubble created
Replication fork = region where parental strands unwound
Single-strand binding proteins = bind to unpaired DNA strands
Topoisomerase = Relieves strain on double helix
Helicase = enzyme that untwist double helix
DNA Replication Complex
DNA replication machine = complex of proteins involved in replication
Replicating DNA Molecule Ends
Telomeres = special nucleotide sequences at end of DNA molecules
Don't contain genes
Postpone DNA shortening at ends of chromosomes
Theorized to be connected to aging
Telomerase synthesizes restoration of telomeres in germ cells
The Basic Principal
DNA Replication = copying of DNA
Watson + Crick came up with concept for replication
Semiconservative model = one strand from parent molecule, one new
Initially untested, later confirmed