10/22/2015fatchiyah, JB UB1 Fatchiyah, Ph.D. Lab. Molecular Biology Brawijaya University

10/22/2015fatchiyah, JB UB2 Chromosome & DNA? Chromosomes, threadlike structures, first observed by Nageli in Walter Flemming was the first to follow the process of mitosis and replication of chromosomes. Thomas Morgan, in his experiments with fruit flies, described genetic recombination, and demonstrated that traits were to inherited together to varying degrees. Alfred Sturtevant extended Morgan’s ideas, used observed recombination rates to produce the first genetic maps.

10/22/2015fatchiyah, JB UB3 Surrounded by a nuclear envelope Perinuclear space Communicates with cytoplasm through nuclear pores The nucleus is the center of cellular operations

10/22/2015fatchiyah, JB UB4 The Nucleus Figure 3.13 Content of nucleus: A supportive nuclear matrix One or more nuclei Chromosomes Chromatin DNA bound to histones

10/22/2015fatchiyah, JB UB5 What Are Chromosomes? Cytogenetics is the study of chromosomes and the related disease states caused by abnormal chromosome number and/or structure. Chromosomes are complex structures located in the cell nucleus, they are composed of DNA, histone and non- histone proteins, RNA, and polysaccharides. They are basically the "packages" that contain the DNA.

10/22/2015fatchiyah, JB UB6 Normally chromosomes can't be seen with a light microscope but during cell division they become condensed enough to be easily analyzed at 1000X. To collect cells with their chromosomes in this condensed state they are exposed to a mitotic inhibitor which blocks formation of the spindle and arrests cell division at the metaphase stage What Are Chromosomes?

10/22/2015fatchiyah, JB UB7 Type of chromosome structure Metacentric Chrom. 1 Acrocentric Chrom. 14 Submetacentric Chrom. 9 1.The short arm is designated as p and the long arm as q. 2.The centromere is the location of spindle attachment and is an integral part of the chromosome. 3.It is essential for the normal movement and segregation of chromosomes during cell division. The ideogram is basically a "chromosome map" showing the relationship between the short and long arms, centromere (cen), and in the case of acrocentric chromosomes the stalks (st) and satellites (sa). The specific banding patterns are also illustrated. Each band is numbered to aid in describing rearrangements.

10/22/2015fatchiyah, JB UB8 Figure 3.14 Chromosome Structure Figure 3.14

10/22/2015fatchiyah, JB UB9 Organization of Genes on Human Chromosome

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10/22/2015fatchiyah, JB UB11 Structural Organization of the Nucleosome

10/22/2015fatchiyah, JB UB12 Structural Organization of the Nucleosome

10/22/2015fatchiyah, JB UB13 Nucleosome Disruption Figure A cyclic mechanism for nucleosome disruption and re-formation. According to this model, different chromatin remodeling complexes disrupt and re-form nucleosomes, although, in principle, the same complex might catalyze both reactions. The DNA-binding proteins could function in gene expression, DNA replication, or DNA repair, and in some cases their binding could lead to the dissociation of the histone core to form nucleosome- free regions of DNA like those illustrated in Figure (Adapted from A. Travers, Cell 96: , 1999.)Figure 4-30

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10/22/2015fatchiyah, JB UB17 Chromosome Facts number of chromosomes: 22 pairs + 1 pair sex-determining chromosomes = 46 –one chromosome of each pair donated from each parent’s egg or sperm –sex chromosomes: X,Y for males; X,X for females –largest chromosome #1 = ~263 million base pairs (bp) –smallest chromosome Y = ~59 million bp

10/22/2015fatchiyah, JB UB18 Chromosomes can be “painted” for easy identification. By technique of multiplex fluorescence in situ hybridization (M-FISH)

10/22/2015fatchiyah, JB UB19 Mitotic chromosomes G1 chromosomes

10/22/2015fatchiyah, JB UB20 Gene Facts size of human genome: 3.4 billion base pairs (bp) number of human genes: ~100,000 genes vary in length and can cover thousands of bases –avg. size: ~3,000 bp only about 5% of the human genome contains genes function of much of the genome is unknown

10/22/2015fatchiyah, JB UB21 Chromosomes come in pairs Humans have 23 pairs of chromosomes –Total of 46 chromosomes Fruit flies have 4 pairs of chromosomes –Total of 8 chromosomes

10/22/2015fatchiyah, JB UB22 Normal Chromosomes Normal human somatic cells have 46 chromosomes: 22 pairs, or homologs, of autosomes (chromosomes 1-22) and two sex chromosomes. This is called the diploid number. Females carry two X chromosomes (46,XX) while males have an X and a Y (46,XY). Germ cells (egg and sperm) have 23 chromosomes: one copy of each autosome plus a single sex chromosome. This is referred to as the haploid number. One chromosome from each autosomal pair plus one sex chromosome is inherited from each parent. Mothers can contribute only an X chromosome to their children while fathers can contribute either an X or a Y.

10/22/2015fatchiyah, JB UB23 Chromosomes of human Male Female Y-chrom

10/22/2015fatchiyah, JB UB24 Members of a chromosome pair Cells with PAIRS of chromosomes are diploid –di – means “two”, “double”, “twice” –oid – “appearance” The two members of any chromosome pair are called homologues, or a homologous pair Ex: –The two “number 1” chromosomes are homologues –The two “number 21” chromosomes are homologues.

10/22/2015fatchiyah, JB UB25 In sexual reproduction new organisms (zygotes) are formed by the joining together of two sex cells (gametes): – a sperm cell from a male and –an egg cell from a female

10/22/2015fatchiyah, JB UB26 What would happen if……. a human egg cell had 46 chromosomes AND a human sperm cell had 46 chromosomes? 46 chromosomes +46 chromosomes 92 chromosomes Too many for a human!

10/22/2015fatchiyah, JB UB27 Diploid organisms need…. A way to produce sex cells (eggs and sperm) that only have ONE member of each chromosome pair In humans, sex cells each have 23 chromosomes –ONE member of each homologous pair –Half of amount of chromosome is named genome (haploid)

10/22/2015fatchiyah, JB UB28 23 chromosomes +23 chromosomes 46 chromosomes Just right for a human!

10/22/2015fatchiyah, JB UB29 The different possibilities of the way chromosomes will separate into gametes helps create genetic diversity OR

10/22/2015fatchiyah, JB UB30 Effect of Crossing Over Crossing over occurs when homologous chromosomes pair with each other before the first meiotic division Chromatids cross over one another, and the crossed sections of the chromatids are exchanged.

10/22/2015fatchiyah, JB UB31 Chromosomes Figure Two closely related species of deer with very different chromosome numbers. In the evolution of the Indian muntjac, initially separate chromosomes fused, without having a major effect on the animal. These two species have roughly the same number of genes. (Adapted from M.W. Strickberger, Evolution, 3rd edition, 2000, Sudbury, MA: Jones & Bartlett Publishers

10/22/2015fatchiyah, JB UB32 The emphasis in the human genome Human 26,588 genes The nervous system The immune system The blood system Signaling and cell-cell communication Programmed cell death Arabidopsis 25, 498 genes Missing Different Missing

Structure of Chromosome - NORs Interphase nucleus of onion root tip through light microscope nucleolus

Structure of Chromosome - NORs electron micrograph of interphase cell from bat pancreas nucleolus

Polytene Chomosome of Drosophila as Giant chromosome

10/22/2015fatchiyah, JB UB36 Phase-contrast image of Drosophila melanogaster polytene cromosomes. A. The end of the X-chromosome is marked with an arrow. Chromocentre is in the upper right corner. B. Shows a magnification of chromomere and interchromomere bands Polytene chromosome

10/22/2015fatchiyah, JB UB37 W-chromosome Yeast Artificial Chromosome

10/22/2015fatchiyah, JB UB38 Bacterial Artificial Chromosome Manipulation by Homologous Recombinant (HeintZ, 2001)

Metaphase: Chromosome in middle cell

Antibodies of a person with an autoimmune disease stain centromers