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The Content of the Genome. 3.6 Genes Show a Wide Distribution of Sizes. Most genes are uninterrupted in yeasts, but are interrupted in higher eukaryotes. Figure 3.10. 4.3 Individual Genomes Show Extensive Variation. Polymorphism 多型性 may be detected:
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Ex Biochem c4-genome 3.6 Genes Show a Wide Distribution of Sizes • Most genes are uninterrupted in yeasts, but are interrupted in higher eukaryotes. Figure 3.10
Ex Biochem c4-genome 4.3 Individual Genomes Show Extensive Variation • Polymorphism多型性 may be detected: • at phenotypic level when a sequence affects gene function (phenotype 表現型） • at the restriction fragment level when it affects a restriction enzyme target site • at the sequence level by direct analysis of DNA (genotype 基因型） • The alleles of a gene show extensive polymorphism at the sequence level • Many sequence changes do not affect function.
Ex Biochem c4-genome Figure 4.1
Ex Biochem c4-genome 4.4 RFLPs and SNPs Can Be Used for Genetic Mapping • RFLP: Restriction fragment length polymorphism
Ex Biochem c4-genome Figure 4.3
Ex Biochem c4-genome Single nucleotide polymorphism (SNP)單核甘酸多型性 • can affect how humans develop diseases, respond to pathogens, chemicals, drugs, vaccines... • Personalized medicine • comparing regions of the genome between cohorts
Ex Biochem c4-genome RFLPs and SNPs • RFLPs and SNPs: • can be the basis for linkage maps • are useful for establishing parent–progeny relationships
Ex Biochem c4-genome Application to exercise science • Identification of performance-related genes • Identification of performance-related genotypes • Talent scouting at molecular level • Practical application?
Ex Biochem c4-genome Genes may affect performance, fitness Rankinen T, MSSE, 2006
Ex Biochem c4-genome Bray MS, MSSE, 2009
Ex Biochem c4-genome 4.5 Why Are Genomes So Large? • There is no good correlation between genome size and genetic complexity. Figure 4.5
Ex Biochem c4-genome 4.5 Why Are Genomes So Large? • increase in the minimum genome size required to make organisms of increasing complexity. • wide variations in the genome sizes of organisms within many phyla. Figure 4.6
Ex Biochem c4-genome 4.6 Eukaryotic Genomes Contain Nonrepetitive & Repetitive DNA Sequence • The kinetics of DNA reassociation after a genome has been denatured distinguish sequences by their frequency of repetition in the genome. • Genes are generally coded by sequences in nonrepetitive DNA.
Ex Biochem c4-genome • Larger genomes within a phylum do not contain more genes. • They do have large amounts of repetitive DNA. • A large part of repetitive DNA may be made up of transposons. Figure 4.8
Ex Biochem c4-genome 4.7 Genes Can Be Isolated by the Conservation of Exons • Conservation of exons can be used as the basis for identifying coding regions: • By identifying fragments whose sequences are present in multiple organisms Figure 4.10
Ex Biochem c4-genome 4.9 Organelles Have DNA • Mitochondria and chloroplasts have genomes that show non-Mendelian inheritance. • Typically they are maternally inherited. Figure 4.15
Ex Biochem c4-genome • Organelle genomes may undergo somatic segregation in plants. • Comparisons of mitochondrial DNA suggest that humans are descended from a single female who lived 200,000 years ago in Africa. Figure 4.14
Ex Biochem c4-genome 4.10 Organelle Genomes Are Circular DNAs That Code for Organelle Proteins • Organelle genomes are usually (but not always) circular molecules of DNA. • Organelle genomes code for some, but not all, of the proteins found in the organelle. Figure 4.16
Ex Biochem c4-genome 4.11 Mitochondrial DNA Organization Is Variable • Animal cell mitochondrial DNA is extremely compact and typically codes for: • 13 proteins • 2 rRNAs • 22 tRNAs Figure 4.17
Ex Biochem c4-genome 4.13 Mitochondria Evolved by Endosymbiosis Figure 4.20
Ex Biochem c4-genome Results from Human Genome Project人類基因體計畫 • The human genome contains 3164.7 million chemical nucleotide bases (A, C, T, and G). • The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases. • The total number of genes is estimated at 30,000 • much lower than previous estimates of 80,000 to 140,000 • Almost all (99.9%) nucleotide bases are exactly the same in all people. • The functions are unknown for over 50% of discovered genes.
Ex Biochem c4-genome Results from Human Genome Project • Humans share most of the same protein families with worms, flies, and plants • but the number of gene family members has expanded in humans, especially in proteins involved in development and immunity • about 1.4 million locations where single-base DNA differences (SNPs) occur in humans
