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The Content of the Genome
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Ex Biochem c4-genome
3.6 Genes Show a Wide
Distribution of Sizes
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Most genes are uninterrupted in yeasts, but are
interrupted in higher eukaryotes.
Figure 3.10
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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
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Many sequence changes do not affect function.
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Ex Biochem c4-genome
Figure 4.1
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Ex Biochem c4-genome
4.4 RFLPs and SNPs Can Be
Used for Genetic Mapping

RFLP: Restriction fragment length
polymorphism
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Ex Biochem c4-genome
Figure 4.3
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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...
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Personalized
medicine
comparing regions
of the genome
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Ex Biochem c4-genome
RFLPs and SNPs

RFLPs and SNPs:
can be the basis for linkage maps
 are useful for establishing parent–progeny
relationships
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Ex Biochem c4-genome
Application to exercise science
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Identification of performance-related genes
Identification of performance-related
genotypes
Talent scouting at molecular level
Practical application?
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Ex Biochem c4-genome
Genes may affect performance, fitness
Rankinen T, MSSE, 2006
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Ex Biochem c4-genome
Bray MS, MSSE, 2009
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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?
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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
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Ex Biochem c4-genome
4.6 Eukaryotic Genomes Contain
Nonrepetitive & Repetitive DNA Sequence
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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.
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Ex Biochem c4-genome
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Larger genomes within
a phylum do not contain
more genes.
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Figure 4.8
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They do have large
amounts of repetitive
DNA.
A large part of repetitive
DNA may be made up
of transposons.
Ex Biochem c4-genome
4.7 Genes Can Be Isolated by
the Conservation of Exons
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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
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4.9 Organelles Have DNA
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Mitochondria and chloroplasts
have genomes that show nonMendelian inheritance.

Typically they are maternally
inherited.
Figure 4.15
Ex Biochem c4-genome
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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
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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:
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13 proteins
2 rRNAs
22 tRNAs
Figure 4.17
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4.13 Mitochondria
Evolved by Endosymbiosis
Ex Biochem c4-genome
Figure 4.20
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Ex Biochem c4-genome
Results from Human Genome Project
人類基因體計畫
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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
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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.
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Ex Biochem c4-genome
Results from Human Genome Project
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Humans share most of the same protein
families with worms, flies, and plants
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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
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