genomesgenomes chapter 21. genomes sequencing of dna human genome project 1990-2003 6 countries 20...
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GenomesGenomesGenomesGenomes
Chapter 21Chapter 21
Genomes• Sequencing of DNA• Human Genome Project• 1990-2003• 6 countries• 20 research centers
Genome• J. Craig Venter in 1992• Whole-genome shotgun
approach• Sequences random DNA
fragments directly
Fig. 21-3-3Fig. 21-3-3
Cut the DNAinto overlappingfragments short enoughfor sequencing
1
2
3
4
Clone the fragmentsin plasmid or phagevectors.
Sequence eachfragment.
Order thesequences intoone overallsequencewith computer software.
Genomes• Complete genome sequences • Human, chimpanzee, • E. coli, brewer’s yeast• Nematode, fruit fly, house mouse,
Genomes• Genomics:• Study of whole sets of genes & their
interactions• Bioinformatics:• Application of computers• Storage & Analysis of biological data
Genomes• Metagenomics• DNA• Entire groups of species • Environmental sample• Sequenced • Human “microbiome”
Figure 21.1Figure 21.1Figure 21.1Figure 21.1
Genomes • Comparison • Evolutionary history of genes• Taxonomic groups
Genome• Phenotype to genotype• Red eye fruit flies (w+w or w+w+)• Computer analysis of genome • Identifies sequences likely to
encode proteins• Genotype to phenotype
Genomes
Genome• NCBI• Genbank• BLAST• Compare DNA Sequences• Compare predicted protein
sequences• Domains (known aa sequences)
Fig. 21-4Fig. 21-4
tatggagaga ataaaagaac tgagagatct aatgtcgcag tcccgcactc gcgagatact 61 cactaagacc actgtggacc atatggccat aatcaaaaag tacacatcag gaaggcaaga 121 gaagaacccc gcactcagaa tgaagtggat gatggcaatg agatacccaa ttacagcaga 181 caagagaata atggacatga ttccagagag gaatgaacaa gggcaaaccc tctggagcaa 241 aacaaacgat gctggatcag accgagtgat ggtatcacct ctggccgtaa catggtggaa 301 taggaatggc ccaacaacaa gtacagttca ttaccctaag gtatataaaa cttatttcga 361 aaaggtcgaa aggttgaaat atggtacctt cggccctgtc cacttcagaa atcaagttaa 421 aataaggagg agagttgata caaaccctgg ccatgcagat ctcagtgcca aggaggcaca 481 ggatgtgatt atggaagttg ttttcccaaa tgaagtgggg gcaagaatac tgacatcaga 541 gtcacagctg gcaataacaa aagagaagaa agaagagctc caggattgta aaattgctcc 601 cttgatggtg gcgtacatgc tagaaagaga attggtccgt aaaacaaggt ttctcccagt 661 agccggcgga acaggcagtg tttatattga agtgttgcac ttaacccaag ggacgtgctg 721 ggagcagatg tacactccag gaggagaagt gagaaatgat gatgttgacc aaagtttgat 781 tatcgctgct agaaacatag taagaagagc agcagtgtca gcagacccat tagcatctct 841 cttggaaatg tgccacagca cacagattgg aggagtaagg atggtggaca tccttagaca 901 gaatccaact gaggaacaag ccgtagacat atgcaaggca gcaatagggt tgaggattag 961 ctcatctttc agttttggtg ggttcacttt caaaaggaca agcggatcat cagtcaagaa
Genome• Proteomics:• Systematic study of all proteins
encoded by a genome• Proteins carry out most of the
cell’s activities
Application• Finding DNA sequence of
organisms• Predict structure & function of new
proteins & RNA sequences• Families of related proteins• Phylogenic trees evolutionary
relationships
Application• The Cancer Genome Atlas project• Monitors 2,000 genes in cancer
cells for changes• Mutations & rearrangements• Lung, ovarian and glioblastoma• Compare to normal cells
Application• DNA sequencing • Highlight diseases • Specialize tx
Genome size• Bacteria range from 1 to 6
million base pairs (Mb)• Eukaryotes usually larger• Humans have 3,200 Mb
Table 21-1Table 21-1
Fig. 21-UN1Fig. 21-UN1
Bacteria Archaea
Genomesize
Number of genes
Genedensity
Most are 1–6 Mb
1,500–7,500
Higher than in eukaryotes
Introns None inprotein-codinggenes
OthernoncodingDNA
Very little
Present insome genes
Can be large amounts;generally more repetitivenoncoding DNA inmulticellular eukaryotes
Unicellular eukaryotes:present, but prevalent onlyin some speciesMulticellular eukaryotes:present in most genes
Lower than in prokaryotes(Within eukaryotes, lowerdensity is correlated with larger genomes.)
5,000–40,000
Most are 10–4,000 Mb, buta few are much larger
Eukarya
Genome• Gene density:• Number of genes in a given length of DNA• Humans & other mammals-lowest • Multicellular eukaryotes have many
introns
• “Junk DNA”
Genome• Genomes of humans, rats, & mice
• 500 noncoding regions-are the same
• 98.5% of the genome does not code for proteins, rRNAs, or tRNAs
• 24% regulatory sequences & introns
Fig. 21-7Fig. 21-7Exons (regions of genes coding for protein
or giving rise to rRNA or tRNA) (1.5%)
RepetitiveDNA thatincludestransposableelementsand relatedsequences(44%)
Introns andregulatorysequences(24%)
UniquenoncodingDNA (15%)
RepetitiveDNAunrelated totransposableelements (15%)
L1sequences(17%)
Alu elements(10%)
Simple sequenceDNA (3%)
Large-segmentduplications (5–6%)
Genome • Pseudogene:• Former genes, mutated• Repetitive genes:• Sequences in multiple copies
Genome• Transposable elements:• DNA that move from one site to
another• Prokaryotes & eukaryotes• Barbara McClintock
Fig. 21-8Fig. 21-8
Genome• Eukaryotic transposable
elements• 1. Transposons:• Move within a genome • DNA intermediate• 2. Retrotransposons:• Move - RNA intermediate
Fig. 21-9aFig. 21-9a
TransposonNew copy oftransposon
DNA ofgenome Transposon
is copiedInsertion
Mobile transposon
(a) Transposon movement (“copy-and-paste” mechanism)
Fig. 21-9bFig. 21-9b
RetrotransposonNew copy of
retrotransposon
Reversetranscriptase
Insertion
RNA
(b) Retrotransposon movement
Genome• Alu elements• 10% of genome• Transposable elements• 300 nucleotides• Do not code for protein• Code for RNA
Genome• Line-1 or L1• 17% genome• Retrotransposons • 6500 nucleotides• Low transposition• Regulate gene expression• Developing neurons
Genome• Repetitive DNA not transposons• 15% • 1. Long sequences of DNA • 2. Simple sequence DNA • Many copies of repeated short
sequences• GTTACGTTACGTTACGTTACGTTAC
Genome• Short tandem repeat (STR)• Repeating units of 2 to 5
nucleotides• Vary among individuals• Centromeres• Telomeres
Genome• Multigene families:• Collections of identical or very similar
genes on a haploid set of chromosomes• Example: • Code for rRNA products• Single transcript makes all rRNA molecules• Transcript sequence repeated many times
Fig. 21-10aFig. 21-10a
(a) Part of the ribosomal RNA gene family
18S
28S
28S18S 5.8S
5.8S
rRNA
DNA
DNARNA transcripts
Nontranscribedspacer Transcription unit
Genome• Nonidentical genes• Hemoglobin• Chromosome 16-α globulin• Chromosome 11-ß globulin• Code separately• Animal development
Fig. 21-10bFig. 21-10b
(b) The human -globin and -globin gene families
Heme
Hemoglobin
-Globin
-Globin
-Globin gene family-Globin gene family
Chromosome 16 Chromosome 11
21
2
1
G A
Embryo Embryo FetusFetus
and adult Adult
Evolution• Human & chimpanzee genomes differ by
1.2%• More Alu elements in humans• Several genes are evolving faster in
humans• Genes involved in defense against malaria
and tuberculosis• Gene that regulations brain size• Genes that code for transcription factors
Fig. 21-15Fig. 21-15
Most recentcommonancestorof all livingthings
Billions of years ago4 3 2 1 0
Bacteria
Eukarya
Archaea
Chimpanzee
Human
Mouse
010203040506070
Millions of years ago
Evolution• FOXP2 gene• Vocalization• Mutation causes speech
impairment• 2 aa difference chimps and
humans
Evolution• Humans 23 pairs of chromosomes• Chimpanzees 24 pairs• Humans & chimpanzees diverged from a
common ancestor• 2 ancestral chromosomes fused in humans• Duplications & inversions result from
mistakes during meiotic recombination
Figure 21.11Figure 21.11Figure 21.11Figure 21.11
Telomeresequences
Centromeresequences
Telomere-likesequences
Centromere-likesequences
Humanchromosome
Chimpanzeechromosomes
12
132
Figure 21.12Figure 21.12Figure 21.12Figure 21.12
Human chromosome Mouse chromosomes
16 167 8 17
Figure 21.14Figure 21.14Figure 21.14Figure 21.14
Ancestral globin gene
α2 α1ζ ζ βα2
α1
yθ ϵ βG A
ϵ
β
β
βζ
α
α
α
Duplication ofancestral gene
Mutation inboth copies
Transposition todifferent chromosomes
Further duplicationsand mutations
Evo
luti
on
ary
tim
e
α-Globin gene familyon chromosome 16
β-Globin gene familyon chromosome 11
Figure 21.16Figure 21.16Figure 21.16Figure 21.16
EGF EGF EGF EGF
EGF
F F F F
F
K
K K
Epidermal growthfactor gene with multipleEGF exons
Fibronectin gene with multiple“finger” exons
Plasminogen gene with a“kringle” exon
Portions of ancestral genes TPA gene as it exists today
Exonshuffling
Exonduplication
Exonshuffling
Evolution• Evo-devo• Evolutionary developmental biology• Developmental processes in
multicellular organisms• Genomic information shows minor
differences in gene sequence or regulation
• Results in major differences in form
Evolution• Homeotic genes• Body segments (fruit fly)• 180-nucleotide sequence • Homeobox• Related homeobox sequences have
been found in regulatory genes of yeasts, plants, and even eukaryotes
Fig. 21-17Fig. 21-17
Adultfruit fly
Fruit fly embryo(10 hours)
Flychromosome
Mousechromosomes
Mouse embryo(12 days)
Adult mouse
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