Transcript
Idiogram and KARYOTYPING
Prepared by
SanmaN
karyology
The study of whole sets of chromosomes is sometimes known as karyology.
What is Idiogram ???
Diagrammatic representation of the gametic chromosome set (n) of a species
Used to compare the karyotype of one species with the other
Karyotype is represented diagrammatically showing all the morphological features of chromosomes.
What is Karyotyping
a standard chart of chromosomes isolated from a cell at metaphase arranged in order by size and structure of physical landmark
The basic number of chromosomes in the somatic cells of an individual or a species is called the somatic number and is designated 2n. Thus, in humans 2n = 46. In the germ-line (the sex cells) the chromosome number is n (humans: n = 23)
Why do scientists look at chromosomes??
Scientists can diagnose or predict genetic disorders by looking at chromosomes.
This kind of analysis is used in prenatal testing and in diagnosing certain disorders, such as Down syndrome, or in diagnosing a specific types of
leukemia.
SPECIMENS USED
Peripheral Blood Cultured Skin Fibroblast
Bone Marrow Amniotic Fluid
How are chromosomes classified?
According to the site of the centromere According to size
How are Chromosomes of similar size and shape distinguished from one another?Chromosome Banding (Q banding,G banding C banding, R banding)
CENTROMERE POSITIONS
CENTROMERE POSITIONS
Submetacentric Metacentric
Telocentri Acrocentric
CLASSIFICATION OF CHROMOSOMES FOR KARYOTYPING
Group A: chromosomes 1,2,3 largest
metacentric and submetacentric
Group B: chromosomes 4,5 large submetacentric
Group C: chromosomes 6,7,8,9,10,11,12mediumsubmetacentric
CLASSIFICATION OF CHROMOSOMES FOR KARYOTYPING
Group D: chromosomes 13, 14, 15 medium acrocentric
Group E: chromosomes 16, 17, 18 short metacentric or submetacentric
Group F: chromosomes 19, 20 short metacentric
Group G: chromosomes 21, 22 very short acrocentric
Preparing a Karyotype
Incubate 3-4 days
Add chemical to stop mitosis in metaphase
Lymphocytes are harvested and treated with hypotonic solution
Swollen cells are fixed, dropped in a glass slide, dried and stained
Types of banding
G-banding is obtained with Giemsa stain following digestion of chromosomes with trypsin. It yields a series of lightly and darkly stained bands - the dark regions tend to be heterochromatic, late-replicating and AT rich. The light regions tend to be euchromatic, early-replicating and GC rich. This method will normally produce 300-400 bands in a normal, human genome.
R-banding is the reverse of G-banding (the R stands for "reverse"). The dark regions are euchromatic (guanine-cytosine rich regions) and the bright regions are heterochromatic (thymine-adenine rich regions).
C-banding: Giemsa binds to constitutive heterochromatin, so it stains centromeres.
Q-banding is a fluorescent pattern obtained using quinacrine for staining. The pattern of bands is very similar to that seen in G-banding.
T-banding: visualize telomeres.
Silver staining: Silver nitrate stains the nucleolar organization region-associated protein. This yields a dark region where the silver is deposited, denoting the activity of rRNA genes within the NOR
The human karyotype
The normal human karyotypes contain 22 pairs of autosomal chromosomes and one pair of sex chromosomes. Normal karyotypes
for females contain two X chromosomes and are denoted 46,XX; males have both an X and a Y chromosome denoted 46,XY. Any variation from the standard karyotype may lead to developmental abnormalities.
Karyotype
MALE KARYOTYPE FEMALE KARYOTYPE
Digital karyotyping
Digital karyotyping is a technique used to quantify the DNA copy number on a genomic scale. Short sequences of DNA from specific loci all over the genome are isolated and enumerated.This method is also known as virtual karyotyping.
Chromosomal abnormalities that can be detected by karyotyping
Autosomal Sex chromosomal
Nmerical Abration
Euploidy Monosomy (n) Diploidy (2n) Triploidy (3n) Tetraploidy (4n)
Aneuploidy Hyperploidy
Trisomy (2n+1)
Tetrasomy (2n+2)
Hypoploidy Monosomy (2n-1) Nullsomy (2n-2)
Ploidy
Polyploidy, where there are more than two sets of homologous chromosomes in the cells
Polyploid series in related species which consist entirely of multiples of a single basic number are known as euploid
Polyploidy in lower plants (ferns, horsetails andpsilotales) is also commonIt is not occuring in humans..It indicate genetical abnormality
Aneuploidy
Aneuploidy is a term used to describe a chromosome problem, such as Down syndrome, that is caused by an extra or missing chromosome.
This would give rise to achromosome abnormality such as an extra chromosome or one or more chromosomes lost. Abnormalities in chromosome number usually cause a defect in development. Down syndrome and Turner syndrome are examples of this.
Condition Syndrome
Trisomy-21 Down
Trisomy-18 Edward
Trisomy-13 Patau
Autosomal Syndromes
Sex chromosomal syndrome
XXY Klinefelter
XYY Jacobs
XXX Superfemale
XO Turner
Thank you
M.Sc Human genetics
School of science
Gujrat uni. Ahm
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