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Chapter 16: The Molecular Basis of Inheritance - Coggle Diagram
Chapter 16: The Molecular Basis of Inheritance
Structure of DNA
Sugar-phosphate backbone
Nitrogenous bases: A, T, C, G
Double Helix
Nitrogenous bases: A, T, C, G
C ↔ G (3 H-bonds)
A ↔ T (2 H-bonds)
Antiparallel strands
Complementary base pairing allows accurate replication
DNA Replication
Elongation
Leading strand: continuous synthesis
Lagging strand: made in Okazaki fragments
DNA polymerase III adds nucleotides in 5' → 3' direction
Primase forms RNA primers
DNA polymerase I replaces RNA primers with DNA
DNA ligase seals gaps
Termination
Two identical DNA molecules form
Initiation
Topoisomerase relieves supercoiling
Single-strand binding proteins (SSBPs) stabilize strands
Helicase unwinds DNA
Replication begins at origins of replication
Chromosome Structure
Prokaryotes
Circular chromosome
Single origin of replication
Eukaryotes
Many origins of replication
Linear chromosomes
DNA wrapped around histones → nucleosomes
Chromatin organization levels
30 nm fiber
Looped domains
Nucleosome
Chromosome
Telomeres & Telomerase
Telomeres
Repetitive noncoding DNA at chromosome ends
Protect coding sequences
Telomerase
Extends telomeres
Active in germ cells, some stem cells, many cancer cells