1、,Chapter Five Chromosome Disorders,Jin Fan, ,1. Chromatin and chromosome,Euchromatin: Slightly and evenly stained, non- or low-repetitive DNA regions Heterochromatin: Darkly and unevenly stained, highly repetitive DNA regions,Chromatin in nucleus,Chromatin composition,Double helix,Nucleosome fiber,S

2、olenoid,Interphase nucleus,Chromatin is the basic components in the cell nucleus Composed of DNA, histones and non-histone proteins,From Chromatin to Chromosome,Different mode of chromatin in metaphase Resulted from highly compaction of chromatin:,Cell Cycle,Chromosome Preparation,Cell culture: Peri

3、pheral blood: PHA stimulating Fibroblast from varous cells Bone marrow for leukemia Amniotic fluid cell for fetal diagnosis Colchicine arresting metaphase Harvest a great number of metaphases Hypotonic treatment Chromosome spread preparation Identify each chromosome,scaffold,Telomere,Long Arm,Short

4、Arm,Chromatid,Chromatids, two after S-phase Centromere Long arm and short arm Telomere,2. Chromosome identification,1. Morphology of chromosome Length RL: Relative length, Ch L / total L of a haploid set Position of centromere AI: Arm index, Long arm L( q ) / Short arm L ( p ) CI: Centromere index,

5、q / Ch L,Metacentric Ch. CI: 1/25/8,Submetacentric Ch. CI: 5/87/8,Acrocentric Ch. CI: 7/8,Satellite,Centromere,Metacentric Ch,Submetacentric Ch,Acrocentric Ch,Short Arm,Long Arm,Satellite arm,International System for Human Cytogenetic Nomenclature ISCN, Denver,1. Rl: from large to small Chromosome l

6、ength: from long to short 2. CI: from small to large Centromere position: from low to high 3. Variable heterochromatic region: 1qh, 9qh, 16qh, Yq Satellite and satellite arm of acrocentric chromosomes,2. Banding of chromosome,Q bands: Caspersson (1970) Quinacrine mustard Fluorescence microscopy Brig

7、ht and dim bands,Giemsa bands: Trypsin digestion Giemsa staining Permanent Dark and light bands,G Bands,Reversed bands: Heated, KOH Giemsa staining Permanent Dark and light bands reversed to G bands,R Banding,Heated, KOH Giemsa staining Heterochromatin in the centromeres, long arm of the Y and 1qh ,

8、 9qh and 16qh,C Bands,Nomenclature of human chromosome,Sister chromatids,Short Arm, p,Long Arm, q,Telomere,Zone,Band,Centromere,heterochromatin,Zones and bands of the chromosme,band,zone,arm,Ch,Chromosomes in different stages of phases of cell cycle More detailed analysis,High-resolution bands,Fluor

9、escence In Situ Hybridization （FISH）,Using DNA probe labeled with a certain marker Hybridizing with DNA in chromosomes and nuclei on slides Probes hybridized with the fragment in chromosome are detected by signals from the labeled markers,Ch.,+Probe,Co- (denature),(anneal),Rapid mapping of genes and

10、 sequences in chromosome Detecting small fragment in interphase. Detecting cryptic rearrangements or small deletions Banding could not be detected 4Mb,Fragile Sites,46, Y, fra(X)(q27-28) Non-staining gaps that occasionally observer at charcteristic sites on several chromosomes Depend on growth condi

11、tions Heritable variants,Lable test DNA with green,Hybrized onto male chromosomal preparation,1：1 mixed,Lable normal DNA with red,Comparative Genomic Hybridization (CGH),CGH,Compare the intensity of two fluorochromes along the chromosome set. Detection of duplication or deletion of chromosomal segme

12、nt.,Array CGH，aCGH,Euploid,46,XX,46,XY,arr (12)(pter-qter)1, -12,arr (9)(q12-qter)3, (15)(q12-qter)1, der t(12q;15q),3. Chromosome abnormalities,(1). Numerical chromosomal abnormalities Heteroploidy: A chromosome complement with chromosome number other than 46 Euploidy: A chromosome complement with

13、an exact multiple of the haploid chromosome number Aneuploidy: A chromosome complement with chro-mosome number other than an multiple of the haploid chromosome number,A. Euploidy:Monoploidy and Polyploidy,1N: Monoploidy 23X or 23Y: in parthenogenesis 3N: Triploidy 69, XXX or 69, XXY in partial mole,

14、 aborted fetus and liveborn who does not survive long 4N: Tetraploid 92, XXXX or 92, XXYY in aborted fetus,Triploidy,13-green, 21-red,Triploidy,parthenogenesis,Imprinting: The expression of the phenotype depends on whether the gene or genome inherited from the father or mother.,Loss or gain of chrom

15、osomes (not multiple of a haploidy) Monosomy 2n-1: one instead of a pair of homologous chromosomes Trisomy 2n+1: three instead of a pair of homologous chromosomes,(2). Aneuploidy,Monosomy,Resulted from nondisjunction of the homologous chromosomes (meiosis I) or sister chromatids (mitosis or meiosis II).,Trisomy,a. Monosomy,Almost all monosomy for an entire chromosome is lethal Turners syndrome: 45,X, the only monosomy