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IB Biology 3.2 chromosomes

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IB Biology 2015 curriculum Genetics

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IB Biology 3.2 chromosomes

  1. 1. 3.2 Chromosomes Essential Question: Chromosomes carry genes in a linear sequence that is shared by members of a species. http://41.media.tumblr.com/4c08ea6 94bcf30c5a9d8423187fba2de/tumblr _mx5zd49kWN1qjofuoo1_1280.jpg Stages of Mitosis by Walter Flemming January 1882
  2. 2. Understandings Statement Guidance 3.2.U1 Prokaryotes have one chromosome consisting of a circular DNA molecule. 3.2.U2 Some prokaryotes also have plasmids but eukaryotes do not. 3.2.U3 Eukaryote chromosomes are linear DNA molecules associated with histone proteins. 3.2.U4 In a eukaryote species there are different chromosomes that carry different genes. 3.2.U5 Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes. 3.2 U6 Diploid nuclei have pairs of homologous chromosomes. 3.2 U7 Haploid nuclei have one chromosome of each pair. [The two DNA molecules formed by DNA replication prior to cell division are considered to be sister chromatids until the splitting of the centromere at the start of anaphase. After this, they are individual chromosomes.] 3.2 U8 The number of chromosomes is a characteristic feature of members of a species. 3.2 U9 A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length. [The terms karyotype and karyogram have different meanings. Karyotype is a property of a cell—the number and type of chromosomes present in the nucleus, not a photograph or diagram of them.] 3.2 U10 Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex.
  3. 3. Applications and Skills Statement Guidance 3.2 A1 Cairns’ technique for measuring the length of DNA molecules by autoradiography. 3.2 A2 Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens and Paris japonica. [Genome size is the total length of DNA in an organism. The examples of genome and chromosome number have been selected to allow points of interest to be raised 3.2 A3 Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascaris equorum. 3.2 A4 Use of karyograms to deduce sex and diagnose Down syndrome in humans. 3.2 S1 Use of databases to identify the locus of a human gene and its polypeptide product.
  4. 4. 3.2 U1 Prokaryotes have one chromosome consisting of a circular DNA molecule. • Prokaryotic DNA is circular and is not associated with any histone proteins • There is one copy of each gene except when the cell and its DNA are replicating Bacterial DNA Plasmids
  5. 5. 3.2 U1 Prokaryotes have one chromosome consisting of a circular DNA molecule. https://classconnection.s3.amazonaws.com/730/flashcards/127 6730/jpg/cell_types1330806303645.jpg
  6. 6. 3.2 U.2 Some prokaryotes also have plasmids but eukaryotes do not. http://upload.wikimedia.org/wikipedia/en/6/6c/PBR322_pl asmid_showing_restriction_sites_and_resistance_genes.jpg • Plasmids are small separate (usually circular) DNA molecules located in some prokaryotic cells • Plasmids are also naked (not associated with proteins) and are not needed for daily life processes in the cell. • The genes in plasmids are often associated with antibiotic resistant and can be transferred from one bacterial cell to another. • Plasmids are readily used by scientists to artificially transfer genes from one species to another (ie. Gene for human insulin)
  7. 7. Nucleosome Structure: consist of 8 histones. They help create super coiling of chromatin, which creates a chromosome during cell replication 3.2 U.3 Eukaryote chromosomes are linear DNA molecules associated with histone proteins. http://micro.magnet.fsu.edu/cells/nucleus/images/ chromatinstructurefigure1.jpg
  8. 8. • Eukaryotic chromosomes are linear and are made up of DNA and histone proteins. • Histones are globular shaped protein in which the DNA is wrapped around. • DNA wrapped around 8 histone proteins is called a nucleosome. • The DNA wraps twice around the histone protein core. • Another histone protein is attached to the outside of the DNA strand. This helps maintain the colloidal structure of the nucleosome. • DNA, because of its negative charge is attracted to the positive charge on the amino acids of the histone proteins. 3.2 U.3 Eukaryote chromosomes are linear DNA molecules associated with histone proteins. http://upload.wikimedia.org/wikipedia/commons/ 4/45/Nucleosome_organization.png
  9. 9. 3.2 U4 In a eukaryote species there are different chromosomes that carry different genes. https://s-media-cache- ak0.pinimg.com/originals/4d/d0/7 a/4dd07a61c384abefef3c521bcab 6bad8.jpg http://dxline.info/img/new_ail/chro mosome-4.jpg • Chromosomes are linear, varying in length and in position of the centromere that holds the sister chromatids together. • In humans there are 23 types of chromosomes. Each chromosome carries a specific sequence of genes along the linear DNA molecule. The position where the gene is located is called the locus. Chromosome 1 Chromosome 4 2,000 Genes 1,000 Genes
  10. 10. 3.2 U.5 Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of those genes. https://molecularhelix.files.wordpress.com/2011/07/homolg.gif • Homologous chromosomes are chromosomes within each cell that carry the same genes • One chromosome came from an individual’s mother and one from the father • They have the same shape and size • These chromosomes pair up during meiosis • Even though these chromosomes carry the same genes, they could have different alleles (different versions of the same gene)
  11. 11. 3.2 U6 Diploid nuclei have pairs of homologous chromosomes. • Diploid nuclei have two copies of each type of chromosome. One chromosome comes from the mother and one from the father. • Haploid gametes (sperm and egg) fuse during sexual reproduction which produces zygote with a diploid nucleus • This cell will then divide by mitosis to produce numerous cells, all with a diploid nucleus • Each nucleus has two copies of each gene, accept the sex chromosomes
  12. 12. 3.2 U.7 Haploid nuclei have one chromosome of each pair. [The two DNA molecules formed by DNA replication prior to cell division are considered to be sister chromatids until the splitting of the centromere at the start of anaphase. After this, they are individual chromosomes.] • Haploid nuclei have one copy of each chromosome or one full set of the chromosomes in that particular species eg. Human 23 chromosomes • These are called gametes, which are sperm and egg • Human sperm and eggs each contain 23 chromosomes https://classconnection.s3.amazonaws.com/116215/flashcards/771420/png/meiosis-1.png
  13. 13. 3.2 U.7 Haploid nuclei have one chromosome of each pair. [The two DNA molecules formed by DNA replication prior to cell division are considered to be sister chromatids until the splitting of the centromere at the start of anaphase. After this, they are individual chromosomes.] • Chromosome to the right splits at the centromere. • This occurs during Anaphase • The chromatids move to opposite poles of the cell to become chromosomes in a newly created cell. Chromosome With two Chromatids Become Two Chromosome
  14. 14. 3.2 U.8 The number of chromosomes is a characteristic feature of members of a species. • The chromosome number is a characteristic feature of that species. • A chromosome number does not indicate how complicated an organism might be • Organisms with different numbers of chromosomes would unlikely be able to interbreed • Chromosome number tends to remain unchanged over millions of years of evolution; however, sometimes through evolution chromosomes can fuse together or split to change the number of chromosomes an organism contains • During human evolution, two ancestral ape chromosomes fused to produce human chromosome 2
  15. 15. 3.2 U.9 A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length. [The terms karyotype and karyogram have different meanings. Karyotype is a property of a cell— the number and type of chromosomes present in the nucleus, not a photograph or diagram of them.] http://upload.wikimedia.org/wikipedia/commons/f/f3/Mapa_gen%C3%A9tico_o_cariograma.jpeg
  16. 16. Karyotyping •A karyotype is a picture of an organism's genetic make-up in which the chromosomes of a cell have been stained so that the banding pattern of the chromosomes appear. •Cells in Metaphase are stained to show distinct parts of the chromosomes. The cells are then photographed through a microscope and enlarged. •The chromosomes are cut from the photograph and arranged according to size, shape, centromere position, and banding patterns. http://www.mrothery.co.uk/module2/images/Image214.gif
  17. 17. 3.2 U.10 Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex. • The X and Y chromosome determine the sex of an individual • The X chromosome contains over 2000 genes in comparison to the Y chromosome has less then 100 genes • If an individual has two X chromosomes they will be a female and if they have an X and a Y chromosome they will be a male • All other chromosomes are called autosomes and do not affect the sex of an individual • The X chromosome has many genes located on it essential to human development, while the Y chromosome has a small number of genes (some of these are shared with the X chromosome). The rest of the genes on the Y chromosome are only necessary for male development http://images.zeit.de/wissen/gesundheit/2014 -01/y-chromosom/y-chromosom-540x304.jpg
  18. 18. 3.2 A.1 Cairns’ technique for measuring the length of DNA molecules by autoradiography. • Using the technique of autoradiography Cairns first supplied the cells with suitable radioactive material (replaces normal hydrogen in thymidine). • Used to selectively label only DNA and will not label RNA. • Intact bacterial chromosomes are placed on slides. These slides are then covered by photographic emulsion and stored in dark. • During this storage the particles are emitted exposing the film • The photographs show the regions of labelled DNA. • The results demonstrated semi- conservative mode of replication.
  19. 19. 3.2 A.2 Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens and Paris japonica. [Genome size is the total length of DNA in an organism. The examples of genome and chromosome number have been selected to allow points of interest to be raised Name Genome Length (million base pairs) Number of Genes T2 phage (Virus) 0.18 300 Escherichia coli (Bacteria) 5 4,377 Drosophila melanogaster (Fruit Fly) 140 17,000 Paris japonica (Woodland Plant) 150,000 Unknown Homo sapiens (Human) 3,000 19-23,000
  20. 20. 3.2 A.2 Comparison of genome size in T2 phage, Escherichia coli, Drosophila melanogaster, Homo sapiens and Paris japonica. [Genome size is the total length of DNA in an organism. The examples of genome and chromosome number have been selected to allow points of interest to be raised Paris japonica Largest Known Genome
  21. 21. 3.2 A.3 Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascaris equorum. Homo sapiens (46)
  22. 22. 3.2 A.3 Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascaris equorum. Pan troglodytes (48) http://static1.squarespace.com/static/51b89f0ce4b0000660671282/t/540785e0e4b00aec95acf4cb/1409779168825/floandfigan.jpg
  23. 23. 3.2 A.3 Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascaris equorum. Canis familiaris 78 https://c1.staticflickr.com/5/4007/5076413065_6a42962771_b.jpg
  24. 24. 3.2 A.3 Comparison of diploid chromosome numbers of Homo sapiens, Pan troglodytes, Canis familiaris, Oryza sativa, Parascaris equorum. Species Name Number of Chromosomes Homo sapiens 46 Pan troglodytes 48 Canis familiaris 78 Oryza sativa 24 Parascaris equorum 2 Rice: Oryza sativa http://upload.wikimedia.org/wikipedia /commons/6/65/Oryza_sativa_Kyoto_J PN_001.JPG Round Worm: Parascaris equorum http://www.vetnext.com/fotos/quizc2a4.jpg
  25. 25. Normal Male 3.2 A.4 Use of karyograms to deduce sex and diagnose Down syndrome in humans. http://commons.wikimedia.org/wiki/File:NHGRI_human_male_karyotype.png
  26. 26. Normal Female 3.2 A.4 Use of karyograms to deduce sex and diagnose Down syndrome in humans.
  27. 27. Male with Down Syndrome: Trisomy 21; mental deficiencies , as well as physical abnormalities 3.2 A.4 Use of karyograms to deduce sex and diagnose Down syndrome in humans. http://upload.wikimedia.org/wikipedia/commons/6/6f/Trisomie_21_Genom-Schema.gif

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