CHROMOSOME STRUCTURE

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By: yuvrajavi (31 month(s) ago)

important information by A.K. Chhabra from HAU Hisar

By: Naeempbg (31 month(s) ago)

Dear Chabra, I want to have this PPT. Plz allow the downloading and oblige

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By: kandukuri (43 month(s) ago)

sir, I am working as a Professor (plant breeding) in Ag College under Acharya N G ranga Agricultural University. I am at present teaching cytology, cytogenetics and genetics at undergraduate and post gaduate level.So I thought this presentation would help me in teaching. thanks seetharamaiah

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Slide 1: 

Dr. A. K. Chhabra Manju Verma chromosomes structure DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

Slide 2: 

CHROMOSOME Rod shaped,dark stained,nucleoprotein bodies seen during mitosis metaphase. First describe by strausberger in 1975. The name chromosome was given by waldeyer in 1888. Clearly visible only during cell division Composed of thin chromatin threads called chromanemata.

Slide 3: 

DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

Slide 4: 

DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

CHROMOSOME NUMBER : 

CHROMOSOME NUMBER They are mainly two types. 1) Somatic chromosome number (2n). It is the number of chromosome found in somatic, merismatic, tissues of a species. 2) Gametic chromosome number (n). It is one half of the somatic number basically it is the haploid number

Slide 6: 

DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

Chromosome size : 

Chromosome size It shows variation depending upon stage of cell division Longest and thinnest chromosome seen during interphase In prophase decrease in their length with an increase thickness . Smallest chromosome seen during anaphase Longest metaphase chromosome found in trillium (32 micro long ). plant are longer chromosome then animals Smallest chromosome is about 1/80,000 in length

CHROMOSOME MORPHOLOGY : 

CHROMOSOME MORPHOLOGY 1) Chromatid 2) Centromere 3) Telomere 4) Nucleolus organizer region 5) Chromomere

CHROMATID : 

CHROMATID Structural and functional unit of chromosome The two chromatid of chromosome through replication of single chromosome. Non-sister chromatid are formed by chromatid of homologus chromosome. Half chromatids are formed

CENTROMERE : 

CENTROMERE According to position of the centromere. 1. Metacentric. 2. Submetacentric. 3. Telocentric. 4. Subtelocentric. It could be classified as- 1. Localised centromeres 2. Neocentromeres 3. Non- localised centromere. -Polycentric -Holocentromeres

TELOMERE : 

TELOMERE Two ends of chromosome. Highly stable Made up of loops (300 A0) chromatin fibers Maintenance of structural integrity.

NUCLEOLUS ORGANISER REGION : 

NUCLEOLUS ORGANISER REGION It is also called as secondary chromosome Nucleolus formed during telophase. Chromosomal site of ribosomal RNA synthesis. Region between secondary constriction and nearest telomere called satellite. Satellites are attached to short arm of nucleolus organizer.

CHROMOMERE : 

CHROMOMERE Bead like structure – prophase of meiosis. Clearly visible –dipterian giant salivary gland chromosomes. They represents units of DNA replication, RNA synthesis, RNA synthesis. One chromosome represents single gene.

KARYOTYPE : 

KARYOTYPE General morphology of somatic chromosome compliment of an individual. It is two types 1) Perfectly symmetrical. 2) Asymmetrical.

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KARYOTYPE OF HUMAN BEINGS DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

Slide 16: 

(2N) 46 no. (2N) 46 no. 23 no. (1N) 23 no. (2N) 46 no. (2N) DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

HETEROCHROMATIN : 

HETEROCHROMATIN CONSTITUTIVE Form of heterochromatin that usually does not change in nature. It is redundant and present in the proximity of centromeres and telomeres and in the N.O.region .Chromatin are less tightly packed FACULTATIVE It is euchromatin that has been heterochromatinized. It is not redundant and it may or may not be condensed in interphase. Chromatin are more densely packed.

Eukaryotic Chromatin = DNA & Histone Proteins : 

Eukaryotic Chromatin = DNA & Histone Proteins DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

CHEMICAL COMPOSITION : 

CHEMICAL COMPOSITION Chromatin composed of – 1) DNA 2) RNA 3) PROTEIN

Slide 20: 

DNA DNA DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

DNA : 

DNA UNIQUE Base sequence present in single copy per genome. All structural genes except (histones,ribosomal RNA, storage proteins) are made up of unique DNA, In cell vary from 70%(man) to 8%(rye) REPETITIVE Consists of DNA nucleotide or base sequence. Human genome (30%) and rye(92%). Highly repetitive DNA and moderately repetitive DNA.

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DNA (1) DISCLAIMER: Copyright of some of the figures used from internet and different web sites is duly acknowledged. The copyright stands with its original developer. The information has been gathered here for educational purpose and not for any kind of commercial purpose.

RNA : 

RNA Interphase chromatin contains 10% RNA Three types- ribosomal,messenger and transfer-RNA. It constitute 40-60 nucleotide long. It is essential for structural organization of chromatin fibers.

PROTEIN : 

PROTEIN HISTONES It constitute 80% of total chromosomal protein. It is highly heterogeneous class of proteins. Molecular weight ranges from 10000-30000. NON-HISTONES It constitute 20% of total chromosomes mass. There is no definite ratio between the amounts of DNA and non histones protein. It may be 12 to more than 20 different types. It includes DNA and RNA polymerase

STRUCTURE : 

STRUCTURE Typical early model Based on light microscope Basic component is chromonema Chromonema composed of genes and chromatin

Recent model of chromosome : 

Recent model of chromosome Based on data from biochemical and electron microscope. Two different models of chromosome structure based on chromatin fibres Multistranded Folded fiber model

1)Multistranded model : 

1)Multistranded model Each chromatin fiber is 100Ao in diameter Four chromatin fibres coil around each other to form quarter chromatid. Chromatids are formed by coiling of two half chromatids. One half chrmatid (800Ao) is formed by association of two quarter chromatid.

2) Folded fiber model : 

2) Folded fiber model It was proposed by Du Praw in 1965. It contain one DNA double helix which is coated with histone and non histone proteins. Two sister chromatin fibres produced by replication of DNA( interphase) Extensive folding occurs during cell division give rise two sister chromatids.

Organization of Chromatid fibres : 

Organization of Chromatid fibres Packaging of long DNA molecule into unit length of fibers. Production of thick fibers from very thin DNA molecule. The beads-on-a-string ultra structure observed during replication.

DIFFERENT MODELS OF CHROMATIN FIBRES : 

DIFFERENT MODELS OF CHROMATIN FIBRES Coiled DNA model: Proposed by Du Praw Coiled structure coated with chromosomal proteins This A type fibers undergo super coiling to produce B type fiber.

2)Nucleosome-solenoid model : 

2)Nucleosome-solenoid model It was proposed by Kornberg and Thomas in 1974. Chromatin composed of a repeating unit called as nucleosome. Nucleosome consist of- A nucleosome core Linker DNA One molecule of 1HI histone Other associated chromosomal proteins

FUNCTION OF CHROMOSOMES : 

FUNCTION OF CHROMOSOMES It provide genetic information for cellular functions of organisms. It protect genetic material (DNA) from damage during cell division. They ensure a precise distribution of DNA to daughter nuclei during cell division. Chromosomes movement is due to centromeres of chromosomes. Participation in regulation of gene action in eukaryotes.