• No results found

Understanding heterochromatin characterization through chromosome banding

N/A
N/A
Protected

Academic year: 2020

Share "Understanding heterochromatin characterization through chromosome banding"

Copied!
10
0
0

Loading.... (view fulltext now)

Full text

(1)

Journal of Biological Sciences and Medicine

Journal home page: www.jbscim.com

∗ Corresponding author

Email address: r_24ras@rediffmail.com (Dr. Rashmi Srivastava)

11

Review Article

Open Access

Understanding heterochromatin characterization through chromosome

banding

Rashmi Srivastava* and Nidhi Mishra

Department of Zoology, University of Allahabad, Allahabad- 211002, India

Received 3 December 2015; Accepted 17 December 2015; Available online 31 December 2015

Abstract

Since the late 1920s, after its finding as the condensed region of chromatin, heterochromatin has been the subject of interest and widely explored and analyzed for unrevealing its characteristics and functional importance. The advent of several chromosomal banding techniques by the time made this task heterochromatin characterization very simple. These can be enlisted as C-banding, G-Banding; some fluorescence banding techniques such as Q-banding; R-Banding, AgNOR banding and other advanced methods that renders higher resolution to the heterochromatin on the pretreatment to chromosomes with DNA ligands and restriction endonucleases. The molecular cytogenetic methods including fluorescence in situ hybridization and its variations flourished later enhanced the capacity to understand the heterochromatin constitution more specifically at gene level. In this review, a description of various banding techniques used for chromosomal characterization of heterochromatin has been provided with a special emphasis to elucidate the components of eukaryotic heterochromatin.

Keywords: Heterochromatin; Chromosome banding; Giemsa; FISH

Introduction

The whole genetic content of a cell resides into the nucleus where it remains packaged into the thread like structures containing certain histone proteins and various non-histone proteins. These structures have an affinity with colour and known as chromatin bodies as the chromatin word is derived from the latin word = chroma means colour (Flemming 1880a; Waldeyer, 1888). After staining with giemsa, chromatin shows a species specific light and dark colour pattern representing decondensed and condensed regions of the chromosome respectively. The decondensed region was further termed as euchromatin and condensed region which stayed condensed through-out the cell cycle as heterochromatin by Hietz (1928). He

propounded that euchromatin is genicly active, and heterochromatin is genicly passive i.e., the heterochromatic chromosomes contain no genes or somehow passive genes (Heitz 1929). Later, this idea proved to be one of the foundations of several pioneering works in the field of chromatin research. Heterochromatin was further subdivided into constitutive and facultative heterochromatin.

(2)

12

that are silenced during the course of cell cycle (Gall et al. 1971; Gatti and Pimpinelli 1992; Elgin and Reuter 2013). In several organisms, heterochromatin is found at the telomeres and in domains enclosing the centromeres (Alberts et al. 2002). In addition, some species specific heterochromatin regions have also been well-known, for instance the silent-mating-type loci in yeasts and the inactive X chromosome in female mammals (Miele et al. 2009; Heard and Disteche 2006).

Several cytological techniques have been utilized time and again for the characterization of heterochromatin. In the present review, an attempt has been made to summarize the selected banding techniques being used for the identification and characterization of heterochromatin both at cytological and at genetic levels.

Constitutive Heterochromatin

The constitutive heterochromatin is repetitive in nature and forms major constituents of centromeres and the telomeres (White 1973; Bedo 1975; López-Fernández et al. 2004). Constitutive heterochromatin contains satellite DNA, which consists of large numbers of short tandemly repeated sequences such as Alpha- satellite DNA, DNA satellite I, II and III which have an important role in the formation of the highly compact structures of the constitutive heterochromatin (John and Miklos 1979). The constitutive heterochromatin is stable in nature and conserves its heterochromatic properties throughout all stages of development during the cell cycle (Higgs et al. 2007); highly polymorphic because of the instability of the satellite DNA, and this polymorphism may affect the size and localization of the heterochromatin with no apparent phenotypic outcome (Miklos and John 1979). Constitutive heterochromatin is intensely

stained and shows a very high affinity to C-banding technique which is the consequence of the very rapid renaturation of the satellite DNA following denaturation (Hsu 1973). In many organisms, the centromere is embedded in a section of special centric heterochromatin that perseveres throughout the interphase, contains a centromere- specific variant H3 histone CENP-A (centromere protein A) and additional proteins that pack the nucleosomes into particularly dense arrangements forming the kinetochore, required for the attachment of the mitotic spindle (Alberts et al. 2002).

Facultative Heterochromatin

(3)

13

chromatin structures (Lyon 2003). Unlike the constitutive heterochromatin, the facultative heterochromatin is not rich in satellite DNA, non-polymorphic and negatively stained by C-banding (Hsu 1973).

Chromosome Banding for

heterochromatin characterization

The condensation of chromosomes occurs at the metaphase state of the mitotic cycle. The higher order organization of chromosomes constitutes the DNA and proteins which are important genetic end points. Several imaging procedures have been used to read out the chromosomes- for instance light microscopy, fluorescence microscopy and other advanced imaging tools involving fluorescence in situ hybridization (Sumner 1973; Schweizer 1976a, 1976b; Maltempi and Avancini 2001). Different staining techniques facilitate the suitable visualization of chromosomes with the help of these above mentioned imaging techniques that increases the resolution of chromosomes accordingly. The staining procedures have been immensely developed in the past decades and help to study the karyotype of multicellular organisms (Alberts et al. 2002). The applicability of staining methods have improved more with the practice of certain treatments and give rise to a distinct pattern known as banding, producing differential staining along the length of a chromosome hence provide a more specific chromosomal study. Banding techniques provide a better identification of chromosomes because each chromosome is specific and produces distinctive bands from other (Gustashaw 1991).

A plentiful of stains have been used that bind to chromosomes, such as some visible light dyes like Giemsa and Orcein being used in the light microscopy, whereas fluorochromes like the Quinacrine, DAPI, Hoechst, Ethidium bromide etc. used in the

fluorescence microscopy. Most of these stains commonly are the organic compounds having large aromatic groups that bind or intercalate to major or minor grooves of the DNA of chromosomes (Holmquist 1975).

Heterochromatin is an important fragment in the study of genomes of several distinct organisms. Hence, the characterization of heterochromatin of different organisms is one of the intriguing aspects in cytological analysis, owing to which different methods have been developed time and again to characterize them. For example, C-banding, G-Banding, some fluorescence banding techniques such as Q-banding, R-Banding, AgNOR banding, advanced banding methods which provide higher resolution including DNA ligands and restriction endonucleases. However, with the course of time, molecular cytogenetic methods like fluorescence in situ hybridization succeeded as a more specific characterization method of heterochromatin at gene level. Some other advancements include the multicolour FISH, spectral karyotyping etc. Certain banding techniques or procedures used for the characterization of constitutive and facultative heterochromatin of the eukaryotic organisms ranging from dipteran insects, plants and humans are summarized in the Table 1.

It is important to note that all these banding techniques being used for chromosomal analysis depends upon the stages of cell cycle which promises of the resolution of the bands rendering to the chromosome condensation. An overview of these banding procedures used for the characterization of heterochromatin is as follows-

C-Banding

(4)

14

repetitive DNA at the centromeres of the chromosomes, replicates late in the cell

cycle than other chromatin and shows special characteristics of stability under

Table 1: Different banding procedures utilized for the characterization of heterochromatic

regions of the chromosomes

Banding techniques

Stains/compounds/ enzymes

Chromosomal regions References

CH FH Euchromatin

C-banding Giemsa/ Trypsin + +/- - Kaul et al. (1978, 1989); Tewari et al. (1986); Maltempi et al. (1996); Maltempi and Avancini (2000) G- banding Giemsa + + - Maltempi and

Avancini (2000) Q-banding Quinacrine mustard + +/- - Kaul et al. (1978,

1989) LIB Quinacrine mustard/

methylene blue

+ +/- - Bultmann and Mezzanotte (1987); Srivastava et al. (2013)

R-banding Chromomycin A3 or Olivomycin

- - + Schweizer (1976a); Schmid and Guttenbach (1988) N-banding Giemsa/ Silver nitrate + + *** Kaul et al. (1978,

1989) Replication

banding

DAPI/ Hoechst 33258, Ethidium bromide, AO, Actinomycin D,

Mithramycin

+ + - Kaul et al. (1978, 1989); Rai et al. (1985); Tewari et al. (1988)

Counter- staining

DAPI/Actinomycin D + + - Agrawal et al. (2010)

Restriction endonuclease banding

Giemsa/Hind III, Alu I, Hae III, Mbo I, Hpa II, Dpn I, Msp I, Hinf I

+ +/- ** Marchi and

Mezzanotte (1990); Martinez et al. (1994)

FISH Propidium

iodide/ antibiotin/ RAG-FITC

+ - *** Maltempi and Avancini (2000)

FISH= fluorescence in situ hybridization; CH= Constitutive heterochromatin; FH= Facultative heterochromatin; C = C- banding; Q= Quinacrine; G = Giemsa; DAPI = 4'-6-diamidino 2-phenyl indole; H = Hoechst 33258; N= N- banding; LIB=Light Induced Banding; AO=Acridine Orange; RAG-FITC = Rabbit Anti-Goat IgG and fluorescein isothiocyanate; + = presence of band; - = absence of band; +/- = differential staining according to species; **= digestion of euchromatin; ***= euchromatic nucleolar organizer embedded in large blocks of constitutive heterochromatin.

the conditions of heat and chemical exposure (Sumner 1973). This property of tightly condensed heterochromatin is

(5)

15

and all other chromatin remains pale (Lee and Collins 1977; Maltempi and Avancini 2001). The C- banding shows dark staining and had an affinity towards centromeres, telomere and constitutive heterochromatin.

Q-Banding

Q-banding technique includes the staining of chromosome with fluorescent stain- Quinacrine mustard and imaging in fluorescent microscopy for the study of AT-rich sequences on the heterochromatin of chromosomal regions (Ellison and Barr 1972).The regions of the genome in which the bases adenine and thymine were relatively abundant (AT- rich) produce intense fluorescence, while regions containing abundant guanine and cytosine residues (GC- rich) fluoresced more weakly (Caspersson et al. 1969; Comings et al. 1975). Some other fluorescent stains yield similar banding patterns as that of Quinacrine, such as Hoescht 33258, DAPI (4’, 6’-diamidino-2-phenylindole) and diimidazolinophe- nylindole (DIPI) (Schnedl et al. 1977). The Q banding technique is useful for detecting heteromorphisms, predominantly the chromosomal polymorphism.

G-Banding

The Giemsa (G-) banding was introduced for cytological studies that employed the common stain Giemsa subsequent to various chemical and enzymatic treatments like trypsin to remove chromosomal proteins of the air- dried chromosome preparations (Comings et al. 1973). After G- banding, all the chromosome pairs stains in a characteristic light and dark banding pattern, where the dark bands are termed as G bands that nearly correlate to GC or AT base-pair composition and repetitive DNA sequences. The intense, giemsa stained regions found in G-banded chromosomes moderately

corresponds to intense fluorescent regions of Q-banded chromosomes (Ennis 1974).

R-Banding

R-banding is also denoted as the reverse (R-) banding and produces an opposite pattern when compared to G- or Q- banding. GC specific dyes for instance, chromomycin A3 or olivomycin, which specifically stain the gene-rich chromatin, produces fluorescent reverse banding patterns, thus enhancing the ability to visualize small structural rearrangements in some portions of the genome (Schweizer 1976a; Schmid and Guttenbach 1988).The dark and light bands are reversed when the chromosomes are treated with heat, special chemicals or DNA ligands before staining. Reverse banding is applied to improve and enhance the contrast of chromosome banding for a better visualization of sequence specific regions on chromosome. Sometimes, this banding proves to be an advantage over G and Q bands, by facilitating the differentiation between heterochromatic and euchromatic regions of chromosomes.

Light Induced Banding (LIB)

(6)

16

Replication banding

Replication banding is also known as high-resolution banding and involves the applicability of a variety of compounds that intercalate into or bind to the DNA molecule, inhibiting condensation of chromosomes in the dividing cells (Hsu 1973; Cornforth and Bedford 1983; Regen et al. 1994). For example, certain DNA ligands like Hoechst 33258, Ethidium bromide, acridine orange, actinomycin D and Mithramycin that characterize heterochromatic areas of chromosomes (Stokke and Steen 1986; Schweizer 1976b; Tomiyasu and Testa 1988; Leemann and Ruch 1978; Schnedl et al. 1977; Bella et al. 1986; Santos and de Souza 1998; Srivastava and Gaur 2015). Using the replication banding method, both R- and G-banded patterns can be obtained for chromosomal analysis (Schmid and Guttenbach 1988).

Restriction endonuclease banding

Restriction endonucleases/enzymes have been found to digest mitotic chromosomes and produce variable patterns of chromatin staining, with the fact that utmost variability is found at heterochromatic regions of the pericentromeric areas (Bianchi et al. 1985; Marchi and Mezzanotte 1990). Restriction endonuclease banding is beneficial in the study of chromosomal polymorphisms of a population, identification of marker chromosomes and the parental origins of individual homologues (Babu 1988; Martinez-Lage et al. 1994; Moore and Best 2001).

Some additional banding procedures

Some other specified chromosomal banding techniques used in the characterization of heterochromatic regions are- NOR or silver staining (active Nucleolar Organizer Regions), Sister Chromatid exchange (SCE),

G11- banding for the localization of pericentromeric region of chromosome 9, distamycin/ DAPI banding (Funaki et al. 1975; Maltempi et al. 1996; Souza et al. 1998; Das and Khuda-Bukhsh 2007; Baydemir et al. 2015).

Fluorescence in situ hybridization

In this techniques, fluorescent labelled DNA probes for specific sequences are hybridized to fixed chromosomes to locate and enumerate the DNA sequences of interest, and thus called as fluorescence in situ

hybridization (FISH). Apart from fluorescent labelling, other labelling methods, both isotopic and non-isotopic are also used and visualized after fluorescent staining in fluorescence microscope for the specific chromosomal characterization (O’Keefe et al. 1996; Liehr 2009; Geurts and de Jong 2013; Pita et al. 2014). The FISH technique is used to visualize the gene enriched chromosomal regions such as the rDNA or the nucleolar organizer regions of chromosomes (Souza et al. 1998; Maltempi and Avancini 2001).

Conclusion

(7)

17

Conflicts of Interest

All contributing authors declare no conflicts of interest.

Acknowledgements

We would like to thank our teachers and fellow researchers for providing necessary guidance in the course of this study.

References

Agrawal UR, Bajpai N, Tewari RR, Kurahashi H (2010) Cytogenetics of Flesh Flies of the Genus Boettcherisca (Sarcophagidae: Diptera). Cytologia 75(2): 149–155

Alberts B, Johnson A, Lewis J, et al (2002) Molecular Biology of the Cell. 4th edition. New York: Garland Science; The Global Structure of Chromosomes. Available from: http://www.ncbi.nlm.nih.gov/books/NBK26 847/

Babu A (1988) Heterogeneity of heterochromatin of human chromosomes as demonstrated by restriction endonucleases treatment. In: Heterochromatin molecular and structural aspects (ed. R.S. Verma) Cambridge University Press pp. 250-275 Baydemir NA, Demirbas, Y, Gozutok S, Karoz,

AM (2015) Distribution of constitutive heterochromatin and nucleolar organizer regions (NORs) in Mustela nivalis Linnaeus, 1766 (Carnivora, Mustelidae) in Turkey. Caryologia 68 (1): 73-76

Bedo DG (1975) C banding in polytene chromosomes of Simulium ornatipes and S. melatum (Diptera: Simuliidae) Chromosoma 51: 3-291

Bella JL, García de la Vega C, López-Fernández C, Gosálvez J (1986) Changes in acridine orange binding and its use in the characterization of heterochromatic regions. Heredity 57: 79-83

Bianchi MS, Bianchi NO, Pantelias GE, Wolff S (1985) The mechanism and pattern induced by restriction endonucleases in human chromosomes. Chromosoma 91: 131-136 Bultmann H, Mezzanotte R (1987)

Characterization and origin of

extrachromosomal DNA granules in

Sarcophaga bullata. J Cell Sci 88: 327-334 Caspersson T, Zech L, Modest EJ, Foley GE,

Wagh U, Simonsson E (1969) DNA - binding fluorochromes for the study of the organization of the metaphase nucleus. Exp Cell Res 58: 141-151

O’Keefe CL, PE Warburton, AG Matera (1996) Oligonucleotide probes for alpha satellite DNA variants can distinguish homologous chromosomes by FISH. Hum Mol Genet 5 (11): 1793–1799

Comings DE, Kovacs BW, Avelino E, Harris DC (1975) Mechanism of chromosome banding V. Quinacrine banding. Chromosoma 50: 111-146

Comings DE, Avelino E, Okada TA, Wyandt HE (1973) The mechanisms of C- and G-banding of chromosomes. Exp Cell Res 77: 469–493

Cornforth MN, Bedford JS (1983) High-resolution measurement of breaks in prematurely condensed chromosomes by differential staining. Chromosoma 88: 315– 318

Das JK, Khuda-Bukhsh AR (2007) GC-rich heterochromatin in silver stained nucleolar organizer regions (NORs) fluoresces with Chromomycin A3 (CMA3) staining in three species of teleostean fishes (Pisces). Indian J Exp Biol 45(5): 413-8

Elgin SCR, Reuter G (2013) Position-Effect Variegation, Heterochromatin Formation, and Gene Silencing in Drosophila. Cold Spring Harbor Perspectives in Biology; 5(8): a017780. doi:10.1101/cshperspect.a017780 Ellison JR, Barr HJ (1972) Quinacrine

fluorescence of specific chromosome regions: Late replication and high AT content in Samoaialeonensis. Chromosoma 36: 375-390

Ennis TJ (1974) Chromosome structure in

Chilocorus (Coleoptera: Coccinellidae). I. Fluorescent and giemsa banding patterns. Canad J Genet Cytol 16: 651-661

Flemming W (1880a) Beiträge zur Kenntnis der Zelle und ihrer Lebenserscheinungen. Arch f mikr Anat 18: 151-259

(8)

18 Response in Eukaryotic Chromosomes. J

Histochem Cytochem 30: 1289-1292

Funaki K, Matsui S, Sasaki M (1975) Location of nucleolar organizers in animal and plant chromosomes by means of an improved N-banding technique. Chromosoma 49: 357-370

Geurts R, de Jong H (2013) Fluorescent In Situ

Hybridization (FISH) on pachytene chromosomes as a tool for genome characterization. Methods Mol Biol 1069:15-24

Gall JG, Cohen EH, Polan ML (1971) Repetitive DNA sequences in Drosophila. Chromosoma 33: 3 19-44

Gatti M, Pimpinelli S (1992) Functional elements in Drosophila melanogaster heterochromatin. Annu Rev Genet 26: 239-275

Gustashaw KM (1991) Chromosome stains. In The ACT Cytogenetics Laboratory Manual 2nd ed, ed. M.J. Barch. The Association of Cytogenetic Technologists, Raven Press, New York

Holmquist G (1975) Hoechst 33258 fluorescent staining of Drosophila chromosomes. Chromosoma 49: 333-356

Hsu TC (1973) Longitudinal Differentiation of Chromosomes. Ann Rev Genet 7: 153-176 Heard E, Disteche CM (2006) Dosage

compensation in mammals: fine-tuning the expression of the X chromosome. Genes Dev 20 (14): 1848-1867

Heitz E (1928) Das heterochromatin der Moose. 1 JehrbWissBotarik 69: 762-8 18 (Title translation: Heterochromatin of Moss) Heitz E (1929) Heterochromatin,

Chromocentren, Chromomeren (Vorlaufige Mitteilung). Ber Dtsch Bot Ges 47, 274–284 Higgs DR, Vernimmen D, Hughes J, Gibbons R

(2007) Using Genomics to Study How Chromatin Influences Gene Expression. Ann Rev Genom Hum Genet 8: 299-325

John B, Miklos GLG (1979) Functional aspects of satellite DNA and heterochromatin. Int Rev Cytol 58: 1-114

Kaul D, Chaturvedi R, Gaur P, Tewari RR (1978) Cytogenetics of the Genus Parasarcophaga

(Sarcophagidae: Diptera). Chromosoma 68: 73-82

Kaul D, Gaur P, Agrawal UR, Tewari RR (1989) Characterization of Parasarcophaga

heterochromatin. Chromosoma 98: 49-55 Liehr T (2009) Fluorescence In Situ

Hybridization (FISH) Application Guide. Springer, Berlin, 452 pp

Lee CS, Collins L (1977) Q-and C-bands in the metaphase chromosomes of Drosophila nasutoides. Chromosoma 61: 57-60

Leemann U, Ruch F (1978) Selective excitation of mithramycin or DAPI fluorescence on double-stained cell nuclei and chromosomes. Histochem 58(4): 329-34

López-Fernández C, Pradillo E, Zabal-Aguirre M, Fernández JL, García de la VC, Gosálvez J (2004) Telomeric and interstitial telomeric-like DNA sequences in Orthoptera genomes. Genome 47 (4): 757-763

Lyon MF (1998) X-chromosome inactivation: A repeat hypothesis. Cytogenet Cell Genet 80: 133–137

Lyon MF (2003) The Lyon and the LINE hypothesis. Semin Cell Dev Biol 14: 313– 318

Maltempi PPP, Avancini RMP, Pimental SMR (1996) Karyotypic characterization of

Muscina stabulans (Fallen) (Diptera: Muscidae) using conventional staining, silver staining and C-banding. Caryologia 49: 13-20

Maltempi PPP, Avancini RMP (2001) C-banding and FISH in chromosomes of the Blow-Flies Chrysomya megacephala and

Chrysomya putoria (Diptera: Calliphoridae). Mem Inst Oswaldo Cruz Rio de Janeiro 96: 371-377

Marchi A, Mezzanotte R (1990) Inter- and intraspecific heterochromatin variation detected by restriction endonuclease digestion in two sibling species of the

Anopheles maculipennis complex. Heredity 65:135–142

Martinez-lage A, Gonzalez-Tizon A, Mendez J (1994) Characterization of different chromatin types in Mytilus galloprovincialis

L. after C-banding, fluorochrome and restriction endonuclease treatments. Heredity 72: 242–249

(9)

19 Protein-Dependent Long-Range Interactions.

PLoS Genet 5(5): e1000478. doi:10.1371/journal.pgen.1000478

Mekhail K, Moazed D (2010) The nuclear envelope in genome organisation, expression and stability. Nat Rev Mol Cell Biol 11: 317–328

Mezzanotte R, Ferrucci L, Marchi A (1979) Light-induced banding (LIB) in metaphase chromosomes of Culiseta longiareolata

(Diptera: Culicidae). Genetica 51: 149-152 Mezzanotte R, Ferrucci L, Marchi A (1981)

Methylene-blue/ coriphosphine-o/ acridine-orange, chromosomal DNA and visible light: interaction and cytological effects in

Drosophila melanogaster. Genetica 55: 203-207

Miklos GLG, John B (1979) Heterochromatin and Satellite DNA in Man: Properties and Prospects. Am J Hum Genet 31: 264-280 Moore CM, Best RG (2001) Chromosome

Preparation and Banding. Encyclopedia of life science. Nature Publishing Group. John Wiley & Sons, Ltd

Oberdoerffer P, Sinclair D (2007) The role of nuclear architecture in genomic instability and ageing. Nat Rev Mol Cell Biol 8: 692– 702

Pita M, Orellana J, Martínez-Rodríguez P, Martínez-Ramírez A, Fernández-Calvín B, Bella JL (2014) FISH methods in cytogenetic studies. Methods Mol Biol 1094: 109-135

Regen D, Holmquist GP, Richer CL (1994) High-resolution replication bands compared with morphologic G-and R-bands. Advances in human genetics. Springer US, 47-115 Schneider R, Grosschedl R (2007) Dynamics

and interplay of nuclear architecture, genome organization, and gene expression. Genes Dev 21(23): 3027–3043

Schnedl W, Mikelsaar AV, Breitenbach M, Dann O (1977) DIPI and DAPI: fluorescence banding with only negligible fading. Hum Genet 36: 167-172

Sumner AT (1973) Involvement of protein disulphides and sulphydryls in chromosome banding. Exp Cell Res 83: 438–442

Schmid M, Guttenbach M (1988) Evolutionary diversity of reverse (R) fluorescent

chromosome bands in vertebrates. Chromosoma 97(2): 101-14

Schweizer D (1976a) Reverse fluorescent chromosome banding with chromomycin and DAPI. Chromosoma 58: 307-324

Schweizer D (1976b) DAPI fluorescence of plant chromosomes prestained with actinomycin D. Exp Cell Res 102: 408-413 Stokke T, Steen HB (1986) Binding of Hoechst

33258 to chromatin in situ. Cytometry 7(3): 227-34

Souza MJ, Rufas JS, Orellana J (1998) Constitutive heterochromatin, NOR location and FISH in the grasshopper Xyleus angulatus (Romaleidae). Caryologia 51: 73-80

Santos N, de Souza MJ (1998) Use of fluorochromes chromomycin A3 and DAPI to study constitutive heterochromatin and NORs in four species of bats (Phyllostomidae). Caryologia 51 (3-4): 265-278

Schnedl W, Breitenbach M, Mikelsaar AV, Stranzinger G (1977) Mithramycin and DIPI: A pair of fluorochromes specific for GC- and AT-rich DNA respectively. Hum Genet 36 (3): 299-305

Srivastava R, Gaur P, Mishra N (2013) Photo-oxidation and quinacrine fluorescence response in the mitotic chromosomes of the flesh-flies Sarcophaga. Int J Pharma Bio Sci 4(1) (B): 250 – 255

Srivastava R, Gaur P (2015) Revelation of heterochromatin heterogeneity in Sarcophagid chromosomes using DNA ligand Mithramycin. Caryologia 68 (1): 55-60

Talbert PB, Henikoff S (2006) Spreading of silent chromatin: inaction at a distance. Nature Rev Genet 7 (10): 793–803

Tewari RR, Kurahashi H, Rai V (1986) Fluorescence patterns of mitotic and polytene chromosomes of the genus

Boettcherisca (Sarcophagidae: Diptera). Acta Biologia Hungarica 37: Supplementum Second European Congress on Cell Biology, Budapest, Hungary pp 6 (Abs.)

(10)

20 human malignant cells. Stain Technol

63(2):83-91

Waldeyer W (1888) Ueber Karyokinese und ibre

Beziehungen zu den

Befruchtungsvorga¨ngen. Arch f mikr Anat 32: 1-122

Figure

Table 1: Different banding procedures utilized for the characterization of heterochromatic regions of the chromosomes

References

Related documents

Chenopodiaceae family (Fig. It is a small sized plant also called as “Banjer” and originally located in South Europe as an erect annual or biennial herb with tuberous

In March of 2014, The Barack Obama Foundation (Foundation) released a Request for Qualifications (RFQ) intended primarily to solicit responses from institutions of higher

While there is a growing body of research investigating adult tertiary and vocational with literacy and numeracy problems, it is also clear that these problems are evident at a

Assessed areas: Time delay between requesting and receiving data, Needing to register (e.g. in a website) to access data, Accessing and understanding terms of use/ licenses,

While both the ESC/ERS risk strati fi cation tool and the REVEAL 2.0 calculator classify patients into low-, inter- mediate-, and high-risk categories, one advantage of the

Different from MMB, playfair cipher is a diagram substitution cipher which takes two letter from message and replace with two another pair letter, this paper combines

So by not rationing charcoal the general usage leads to unsustainable use.The results relate with a study done by Chris Howorth( 1992 ) in Tanzania on Management of fuel

The govern function encompasses strategic procedures and measures which ensure that allocated IT products and services contribute to the business objectives. In particular,