Lesson 8 Introduction To Karyotyping PDF

INTRODUCTION TO KARYOTYPING KARYOTYPE It is a visual representation of the chromosomes in a cell. It is a cytogenetics technique that studies chromosomes and their abnormalities. Human cells typically have 46 chromosomes organized into 23 pairs. ￭ Each parent contributes one chromos...

INTRODUCTION TO KARYOTYPING KARYOTYPE It is a visual representation of the chromosomes in a cell. It is a cytogenetics technique that studies chromosomes and their abnormalities. Human cells typically have 46 chromosomes organized into 23 pairs. ￭ Each parent contributes one chromosome to each pair. ￭ The first 22 pairs are called autosomes. ￭ The 23rd pair is the sex chromosomes KARYOTYPE Presence or absence of individual chromosomes Nature or extent of chromosomal aberrations Sex chromosome content Describes the number of chromosomes and what they look like under a light microscope. Attention is paid on their length, position of the centromere, banding pattern, any differences between the sex chromosomes, and any other physical characteristics. Genetic counseling allows the parents for an opportunity to determine the genetic odds that their offspring may carry a particular negative or lethal trait Karyotyping Analysis It is a cytogenetic technique used to study the chromosomes of an individual or organism. It involves the visualization and analysis of the chromosomal complement (karyotype) to identify numerical and structural abnormalities. Karyotyping Analysis Sample Collection: The sample is typically obtained from a patient's blood, amniotic fluid, bone marrow, or other tissues. Cell Culture: Cells are cultured to encourage cell division and obtain a sufficient number of cells for analysis. Karyotyping Analysis Cell Harvesting: Cells are harvested from the culture, and a cell suspension is created. Treatment and Fixation: The cell suspension is treated to create metaphase spreads on microscope slides. The cells are fixed to preserve their structure. Karyotyping Analysis Staining: Chromosomes on the slides are stained to make banding patterns visible. Microscopic analysis: A microscope is used to examine the stained chromosomes. Chromosomes are photographed at high magnification. Karyotyping Analysis Analysis and interpretation: Cytogeneticists analyze the karyotype to identify numerical abnormalities (aneuploidies) or structural abnormalities. Reporting: The findings are documented in a report, which is then provided to healthcare professionals for further interpretation and discussion with the patient.  Karyology "Karyology" generally refers to the study of karyotypes and chromosomes Karyology involves the examination and analysis of karyotypes. ￭ Karyogram/Idiogram - is a visual representation or photograph of an individual's or an organism's chromosomes arranged in a standard format, typically based on their size, banding patterns, and other morphological characteristics. Variations in a Chromosome Morphology Deletion: refers to the loss or absence of a part of a chromosome. ￭ Types of Deletions: Terminal Deletion: The deletion occurs at the end of a chromosome. Interstitial Deletion: The deletion occurs within the chromosome, away from the ends. Duplication: refers to the presence of an extra copy of a portion of a chromosome. Variations in a Chromosome Morphology Duplication: refers to the presence of an extra copy of a portion of a chromosome. ￭ Types of Duplications: Tandem Duplication: The duplicated segment is adjacent to the original segment on the same chromosome. Reverse Duplication (Inversion Duplication): The duplicated segment is oriented in the opposite direction to the original segment. Displaced Duplication: The duplicated segment is found elsewhere in the genome. Variations in a Chromosome Morphology Inversion: refers to the reversal of the normal orientation of a chromosome segment. ￭ Pericentric Inversion: Involves the inversion of a chromosomal segment that includes the centromere. ￭ Paracentric Inversion: Involves the inversion of a chromosomal segment that does not include the centromere. Variations in a Chromosome Morphology Translocation: refers to the movement of a segment of one chromosome to another non- homologous chromosome. T ￭ Reciprocal Translocation: two non-homologous chromosomes exchange segments with each other. ￭ Robertsonian Translocation: the long arms of two acrocentric chromosomes (chromosomes with a very short p-arm) fuse together, resulting in a single, larger chromosome.  Variations in a Chromosome Number Polyploidy: is a genetic condition characterized by the presence of more than two complete sets of chromosomes in an organism's cells. Aneuploidy: occurs when there is an excess or deficiency of individual chromosomes, resulting in an unbalanced set.  Variations in a Chromosome Number Monosomy: is a genetic condition characterized by only one copy of a particular chromosome in an otherwise diploid cell. Trisomy: is a genetic condition characterized by the presence of an additional copy of one chromosome, resulting in three copies instead of the usual two.  Variations in a Chromosome Number Euploidy: is a condition in genetics where a cell or organism has a complete and balanced set of chromosomes. Nondisjunction is a genetic event during cell division in which chromosomes fail to separate properly. Nondisjunction results in an uneven distribution of chromosomes between daughter cells, leading to an abnormal number of chromosomes in the affected cells. Karyotype The study of karyotypes is made possible by staining. Usually, a suitable dye, such as Giemsa, is applied after cells have been arrested during cell division by a solution of colchicine. For humans, white blood cells are used most frequently because they are easily induced to divide and grow in tissue culture. Karyotype Chromosomes are arranged into seven groups based on size and centromere location. Chromosome Painting Using Fluorescent Dyes Types of banding G-Banding (Giemsa Banding): It involves staining chromosomes with Giemsa dye, which alternates dark and light bands along the chromosomes. R-Banding (Reverse Banding): It involves using different staining techniques to create a reverse pattern of bands. Types of banding C-Banding (Constitutive Heterochromatin Banding): The C-banding method selectively stains the areas located around the centromeres of all chromosomes and on the distal long arm of the Y chromosome. Q-Banding (Quinacrine Banding): Q-banding involves staining chromosomes with quinacrine mustard. It produces a fluorescent banding pattern, and it is used less frequently than G-banding in clinical settings. Types of banding T-Banding (Telomere Banding): focuses on staining the telomeric regions of chromosomes, which are located at the ends of the chromosomes.