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Chapter 11: An Introduction to Human Genome A linear polynucleotide consisting of four types of monomeric nucleotides Each nucleotide contains: Deoxyribose, a Nitrogenous base, and a Phosphate group Four bases: Adenine (A) Cytosine (C) Guanine (G) Thymine (T) Forensic Biology by Richard Li 2 The Double Helix Watson & Crick B-Form of DNA- right handed turns and two grooves that spiral (major & minor) Stabilized by chemical interactions A always pairs with T C always pairs with G Forensic Biology by Richard Li 3 Denaturation Melting curve Melting Temperature Renaturation (reannealing) Euchromatin Heterochromatin Forensic Biology by Richard Li 4 Human Chromosomes Short arm (p) & Long arm (q) Centromeres- DNA sequences found near the point of attachment of mitotic or meiotic spindle fibers Telomeres- ends of chromosomes Forensic Biology by Richard Li 5 Gametes- spermatozoa and ova ▪ Haploid ▪ 22 autosomes + 1 sex chromosome Somatic Cells- most other cells except reproductive ▪ Diploid ▪ Two copies of each autosome + 2 sex chromosomes= 46 Forensic Biology by Richard Li 6 Human genome one set of 23 chromosomes Contains biological information to perform biological functions Nuclear and Mitochondrial Genomes 3.2 billion base pairs 30,000 – 40,000 genes ▪ Encode information for the synthesis of proteins Human Genome Project (1990)▪ 2.6 billion base pairs (80%) completed Forensic Biology by Richard Li 7 Intergenic Non-coding Sequences 60% of human genome sequence Repetitive DNA ▪ Genome-wide (interspersed repeats) ▪ SINEs, LINEs, LTR ▪ Tandemly repeated DNA ▪ ▪ ▪ ▪ Repeat units that are placed next to each other in an array Satellite DNA Minisatellites Microsatellites Forensic Biology by Richard Li 8 Differences between individual genomes Sequence polymorphism Length polymorphism DNA markers Genetic mapping Forensic DNA profiling Forensic Biology by Richard Li 9 Majority are Single-nucleotide polymorphisms (SNP) Alleles Homozygous Heterozygous Genotype- combination of alleles at any given locus DNA profile Forensic Biology by Richard Li 10