Cytogenetic method

Август 2, 2022

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Биология
Cytogenetic method

Содержание

2. Cytogenetics = The study of chromosome number, structure, function, and behavior in relation to gene inheritance,
3. Chromosome Chromo = colored in response to dye Some = body Chromosome of Eukaryotes have been
4. Why Analyse Chromosomes and Genes? Genetic errors arise from deletions or insertions of genetic material, abnormal
5. Cytogenetic methods to detect chromosomal abnormalities underlying human birth defects usually involve analysis of mitotic chromosome
6. What tissues are appropriate for chromosome study? • A tissue that can be stimulated to undergo
7. The chromosomes are so named as they may be stained by certain dyes Chromosomes are composed
8. Chromosome Sister Chromatides
9. Chromosomes of different species differ in number and information content Humans and several other species of
10. Karyotyping Karyotype A pictorial display of metaphase chromosomes from a mitotic cell Homologous chromosomes- pairs
11. Karyotype Karyotyping is the analysis of chromosomes Cytogenetics is the study of chromosomes and inheritance Cytogenetics
12. Preparing a karyotype Harvested cells are first cltured The cells are then treated with colchicine which
15. The analysis involves comparing chromosomes for their length, the placement of centromeres (areas where the two
17. Metaphase chromosomes
18. Karyotyped chromosomes
20. Banding patterns on human mitotic chomosomes due to regions of condensed chomatin (darker - G bands)
21. Human chromosome number is determined by their length in “mitotic figures"
23. International System for Cytogenetic Nomenclature, (ISCN,1995) Short arm of the chromosome = p Long arm of
24. Hundreds of genes are encompassed within a single G-band. Therefore, most constitutional chromosome abnormalities are associated
25. Conclusion The evolution of cytogenetic techniques and the mapping of the human genome have provided scientists
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Cytogenetics = The study of chromosome number, structure, function, and behavior

in relation to gene inheritance, organization and expression

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Chromosome
Chromo = colored in response to dye
Some = body
Chromosome of Eukaryotes

have been the traditional subject for cytogenetic analysis because they are large
enough to be examined with light microscope

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Why Analyse Chromosomes and Genes? Genetic errors arise from deletions or insertions

of genetic material, abnormal numbers of whole chromosomes or genes, and even from misplacement of a single base in the DNA sequence.
Genetic abnormalities can range from relatively harmless to severe: from vitamin deficiencies and food allergies to cancer, birth defects and infant mortality.

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Cytogenetic methods to detect chromosomal
abnormalities underlying human birth defects usually
involve analysis

of mitotic chromosome

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What tissues are appropriate for chromosome study?
• A tissue that can

be stimulated to undergo cell division in-vitro
• It is only during mitosis of the cell cycle that distinct chromosomes can be visualized with a light microscope
After culturing, in-vitro, a proportion of
cells are arrested in mitosis, and are then “harvested” for chromosome analysis After harvesting, the cell preparations are dropped onto glass slides and stained. For most chromosome analyses, a G-banding technique is utilized for staining.
Metaphase spread

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The chromosomes are so named as they may be stained by

certain dyes
Chromosomes are composed of chromatin, which is composed of protein and DNA
When cells are not dividing, the genetic material is decondensed
Chromosomes become visible as distinct structures when the cell divides

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Chromosome
Sister Chromatides

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Chromosomes of different species differ in number and information content
Humans

and several other species of organisms have 46 chromosomes

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Karyotyping
Karyotype
A pictorial display of metaphase chromosomes from a mitotic cell
Homologous

chromosomes- pairs

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Karyotype
Karyotyping is the analysis of chromosomes
Cytogenetics is the study of

chromosomes and inheritance
Cytogenetics is based on studies of humans as well as Drosophila and other organisms

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Preparing a karyotype
Harvested cells are first cltured
The cells are then

treated with colchicine which arrests the cells in metaphase, and then treated and stained to observe the chromosomes
Chromosomes can be photographed or visualized using a computer, and then analyzed
Chromosomes are identified by size, position of the centromere, and banding and staining regions

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The analysis involves comparing chromosomes for their length, the placement of

centromeres (areas where the two chromatids are joined), and the location and sizes of G-bands.

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Metaphase chromosomes

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Karyotyped chromosomes

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Banding patterns on human mitotic chomosomes
due to regions of condensed chomatin

(darker - G
bands) and less condensed chromatin (lighter - R bands)

human chromosome 4 at varying resolutions due to exact mitotic
stage, (or degrees of spreading - squashing - stretching)

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Human chromosome number is determined by their
length in “mitotic figures"

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International System for Cytogenetic Nomenclature, (ISCN,1995)
Short arm of the chromosome = p
Long

arm of the chromosome = q
Bands are numbered independently on the short and long arms
Centromeres = p10,q10
Band numbers increase as move from the centromere to the telomere

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Hundreds of genes are encompassed
within a single G-band.
Therefore, most constitutional chromosome
abnormalities

are associated with multiple
congenital anomalies.
Therefore, deletion of a single gene cannot be
detected by G-banding.

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Conclusion
The evolution of cytogenetic techniques and the mapping of the human

genome have provided scientists with a great deal of insight into the causes of numerous genetic disorders. Though rooted in early chromosome staining and gene mapping techniques, modern FISH, SKY, and CGH methods have far outshone their predecessors by providing an unprecedented view of human chromosomes.

Cytogenetic method

Содержание

Cytogenetics = The study of chromosome number, structure, function, and behavior

ChromosomeChromo = colored in response to dyeSome = bodyChromosome of Eukaryotes

Why Analyse Chromosomes and Genes? Genetic errors arise from deletions or insertions

Cytogenetic methods to detect chromosomalabnormalities underlying human birth defects usuallyinvolve analysis

What tissues are appropriate for chromosome study?• A tissue that can

The chromosomes are so named as they may be stained by

ChromosomeSister Chromatides

Chromosomes of different species differ in number and information content Humans

KaryotypingKaryotypeA pictorial display of metaphase chromosomes from a mitotic cell Homologous

KaryotypeKaryotyping is the analysis of chromosomes Cytogenetics is the study of

Preparing a karyotypeHarvested cells are first cltured The cells are then