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HUMAN GENOME

HUMAN GENOME. HUMAN GENOME. Gene density 1/100 kb (vary widely); Averagely 9 exons per gene 363 exons in titin gene Many genes are intronsless Largest intron is 800 kb (WWOX gene) Smallest introns 10 bp Largest protein: titin: 38,138 AA. HUMAN GENOME. Interferon genes Histone genes

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HUMAN GENOME

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  1. HUMAN GENOME

  2. HUMAN GENOME • Gene density 1/100 kb (vary widely); • Averagely 9 exons per gene • 363 exons in titin gene • Many genes are intronsless • Largest intron is 800 kb (WWOX gene) • Smallest introns 10 bp • Largest protein: titin: 38,138 AA

  3. HUMAN GENOME • Interferon genes • Histone genes • Many ribonuclease genes • Heat shock protein genes • Many G-protein coupled receptors • Some genes with HMG boxes • Various neurotransmitters receptors and hormone receptors Intronless Genes

  4. HUMAN GENOME • The human genome is the term used to describe the total genetic information (DNA content) in human cells. • It comprises two genomes, a complex nuclear genome, and a simple mitochondrial genome

  5. HUMAN GENOME • Nuclear genome accounts for 99.9995% of the total genetic information. • Mitochondrial genome accounts for the remaining 0.0005%

  6. HUMAN MITOCHONDRIAL GENOME

  7. HUMAN MITOCHONDRIAL GENOME • The human mitochondrial genome is a single circular double-stranded DNA. • Complete nucleotide sequence has been established

  8. HUMAN MITOCHONDRIAL GENOME • 16 569 bp in length • 44% (G + C). • The two DNA strands have significantly different base compositions: the heavy (H) strand is rich in guanines, the light (L) strand is rich in cytosines.

  9. HUMAN MITOCHONDRIAL GENOME H strand enriched in G L strand enriched in C

  10. HUMAN MITOCHONDRIAL GENOME • Very few repeats • No introns • 93% coding; • Recombination not evident

  11. HUMAN MITOCHONDRIAL GENOME • The human mitochondrial genome contains 37 genes. • 28 are encoded by the heavy strand, and 9 by the light strand

  12. HUMAN MITOCHONDRIAL GENOME • Of the 37 genes, 24 specify a mature RNA product: 22 mitochondrial tRNA molecules and two mitochondrial rRNA molecules, • The remaining 13 genes encode polypeptides which are synthesized on mitochondrial ribosomes.

  13. HUMAN MITOCHONDRIAL GENOME Mitochondrial codon table

  14. HUMAN NUCLEAR GENOME • The nucleus of a human cell contains more than 99% of the cellular DNA. • 23 (XX) or 24 (XY) linear chromosomes each of which has histones and other nonhistone proteins bound to it.

  15. HUMAN NUCLEAR GENOME • Introns in the most of the genes • Genes are transcribed individually • Repetitive DNA sequences (45%) • Recombination at least once for each chrom. • Mendelian inheritance (X + auto, paternal Y)

  16. HUMAN NUCLEAR GENOME Chromosome Size (Mbp) 1 249 2 237 3 192 4 183 5 174 6 165 7 153 8 135 9 132 10 132 11 132 12 123

  17. HUMAN NUCLEAR GENOME Chromosome Size (Mbp) 13 108 14 105 15 99 16 84 17 81 18 75 19 69 20 63 21 54 22 57 X 141 Y 60

  18. HUMAN NUCLEAR GENOME Group Chromosomes Description A 1–3 Largest; 1 and 3 are metacentric but 2 is submetacentric B 4,5 Large; submetacentric with two arms very different in size C 6–12,X Medium size; submetacentric D 13–15 Medium size; acrocentric with satellites E 16–18 Small; 16 is metacentric but 17 and 18 are submetacentric F 19,20 Small; metacentric G 21,22,Y Small; acrocentric, with satellites on 21 and 22 but not on the Y

  19. HUMAN NUCLEAR GENOME • Metacentric: Chromosome having its centromere in the middle • Submetacentric: Chromosomes have short and long arms of unequal length with the centromere more towards one end • Acrocentric:Chromosomes have a centromere very near to one end and have very small short arms.

  20. HUMAN NUCLEAR GENOME Repetitive sequence • The human genome is occupied by stretches of DNA sequences of various length that exist in variable copy number. • These repetitive sequences may be in a tandem orientation or they may be dispersed throughout the genome. • Repetitive sequences may be classified by function, dispersal patterns, and sequence relatedness.

  21. HUMAN NUCLEAR GENOME 1. Satellite DNA (tandem repeats) typically refers to highly repetitive sequences with no known function 2. Interspersed repeat sequences Typically the products of transposable element integration, including retrogenes and retropseudogenes of a functional gene.

  22. Satellite DNA HUMAN NUCLEAR GENOME Microsatellites Macrosatellites Minisatellites

  23. HUMAN NUCLEAR GENOME Microsatellites • Small arrays of short simple tandem repeats. • primarily 4 bp or less. • Different arrays are found dispersed throughout the genome, although dinucleotide CA/TG repeats are most common, yielding 0.5% of the genome. • Runs of As and Ts are common as well. • Microsatellites have no known functions.

  24. HUMAN NUCLEAR GENOME Minisatellites • Tandemly repeated sequences of DNA of lengths ranging from 1 kbp to 15 kbp. • For example, telomeric DNA sequences contain 10–15 kb of hexanucleotide repeats. • Most commonly TTAGGG in the human genome, at the termini of the chromosomes.

  25. HUMAN NUCLEAR GENOME Macrosatellites • Very long arrays, up to hundreds of kilobases, of tandemly repeated DNA.

  26. HUMAN NUCLEAR GENOME Transposable Elements (Interspersed repeat sequences) Can be divided into two classes based on the mode of transposition; 1. The class I elements 2. The class II elements

  27. HUMAN NUCLEAR GENOME 1. The class I elements • They are TEs which transpose by replication that involves an RNA intermediate which is reverse transcribed back to DNA prior to reinsertion. • These are called retroelements and include LTR transposons, non-LTR elements (LINEs and SINEs), and retrogenes.

  28. HUMAN NUCLEAR GENOME 2. The class II elements • Class II elements move by a conservative cut-and-paste mechanisms. • The excision of the donor element is followed by its reinsertion elsewhere in the genome.

  29. HUMAN NUCLEAR GENOME • Integration of Class I and Class II transposable elements results in the duplication of a short sequence of DNA, the target site. • There are about 500 families of such transposons. • Most of transposition has occurred via an RNA intermediate, yielding classes of sequences referred to as retroelements (more than 400 families, e.g. Alu, L1, retrogenes, MIR). • However, there is also evidence of an ancient DNA-mediated transposition (more than 60 families of class II (DNA) transposons, e.g. THE-1, Charlie, Tigger, mariner).

  30. HUMAN NUCLEAR GENOME Retroelements • (LINEs) long interspersed repetitive elements and (SINEs) Short interspersed repetitive elements are the two most abundant classes of repeats in human. • Represent the two major classes of mammalian retrotransposons.

  31. HUMAN NUCLEAR GENOME LINEs (long interspersed repetitive elements) • L1, L2, L3 LINE is ~21% of human DNA • A full-length LINE (or L1 element) is approximately 6.1 kbp • There are about 100000 copies of L1 sequences in our • genome. • Approximately 1% of the estimated 3500 full-length LINEs have functional RNA polymerase II promoter sequences along with two intact open reading frames necessary to generate new L1 copies.

  32. HUMAN NUCLEAR GENOME SINE (Short interspersed nuclear elements) • Alu is ~10.7% of human DNA • (1,200, 000 copies) • MIR, MIR3 is 3% of hum DNA (500,000 copies) • Each Alu element is about 280 bp

  33. HUMAN NUCLEAR GENOME LTRs (Long terminal repeats) • ERV and MalR are 8% of human DNA • (500,000 copies)

  34. HUMAN NUCLEAR GENOME • Class II elements contain inverted repeats (10–500 bp) at their termini and encode a transposase that catalyses transposition. • They move by excision at the donor site and reinsertion elsewhere in the genome by a non-replicative mechanism. • MER1 (Charlie), MER2 (Tigger), others • (350, 000 copies) • 2.8% of human DNA

  35. HUMAN GENOME PROJECT • The Human Genome Project is one of the most enterprising and challenging aspects of modern genetic research. • Funded primarily by the US Government, • This project was created to map and sequence the entire human genome--that is, to locate every gene on every human chromosome. • It is estimated that anywhere from 100,000 to 300,000 genes exist! And scientists not only plan to map the genes, but also intend to sequence the 3 billion DNA amino acid “building blocks” that make each gene!

  36. HUMAN GENOME PROJECT • Human genome project was conceived in 1984 and begun in 1990. • Human genome project draft completed in 2001. • These drafts representing only 83-84% of the entire genome. • The Human Genome Project could easily be the most important organized scientific effort of mankind.

  37. HUMAN GENOME PROJECT • The project involves so many people, and not only geneticists; rather the Human Genome Project relies on all scientific and technological backgrounds from physics and chemistry to engineering and robotics to computer science. • Even sociologists, ethicists, and theologians are involved. Never before in the history of humanity have so many professionals united under a single scientific endeavor. • The estimated total cost of the Human Genome Project is a staggering $3 billion • The US government provides most of the funds (other funds coming from big companies and other countries).

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