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)
CLASSIFICATION OF CHROMOSOMES FORKARYOTYPINGGroup A: chromosomes 1,2,3 largestmetacentric and submetacentricGroup B: chromosomes 4,5 large submetacentricGroup C: chromosomes 6,7,8,9,10,11,12 medium submetacentric
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 Add chemical to 3-4 days 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 Rstands for "reverse"). The dark regions areeuchromatic (guanine-cytosine rich regions) andthe bright regions are heterochromatic (thymine-adenine rich regions).C-banding: Giemsa binds toconstitutive heterochromatin, so it stainscentromeres.
Q-banding is a fluorescent pattern obtainedusing quinacrine for staining. The pattern ofbands is very similar to that seen in G-banding.T-banding: visualize telomeres.Silver staining: Silver nitrate stains thenucleolar organization region-associatedprotein. This yields a dark region where thesilver is deposited, denoting the activity of rRNAgenes 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.
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 abnormalitiesthat can be detected bykaryotyping Autosomal Sex chromosomal
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 common It 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.