What Is Chromosome Karyotype Analysis?

Chromosome karyotype analysis is a technique that traditionally involves observing the morphology of chromosomes. In recent years, fluorescence in situ hybridization technology has been used to detect and label specific sites on chromosomes with fluorescent probes, enabling precise detection of single-base mutations in the DNA strands of chromosomes, thereby greatly improving the accuracy of chromosome karyotype analysis.

Chromosomes of different species have their own specific morphological structures (including chromosome length, centromere position, arm ratio, and satellite size), and this morphological feature is relatively stable. By using fluorescence in situ hybridization technology to detect and label specific sites on chromosomes with fluorescent probes, chromosome karyotype analysis can directly read the change in fluorescence signal intensity of the reaction system through a fluorescence detector to directly determine single-base mutations in chromosome DNA strands.

How to read a chromosome karyotype analysis report?

The chromosome karyotype report includes complete karyotype images and descriptions. For us, the most important thing is to understand the results in the "chromosome karyotype" column. For a chromosome report, the most important thing is the conclusion of the chromosome karyotype. In order to facilitate understanding, we roughly divided chromosome karyotype results into three types.

Normal karyotype

• Normal male karyotype is: 46, XY;
  

• Normal female chromosome karyotype: 46, XX.
  

If your chromosome report shows the above two karyotypes, and your sex matches the karyotype, then your chromosomes are completely normal.

Chromosomal variation (chromosomal polymorphism)

Chromosomal variations are also often referred to as chromosomal polymorphisms. The total frequency of various chromosomal variations in the population is about 10% to 15%. Although chromosomal variations appear to be different from normal karyotypes, they have no actual clinical significance. Therefore, chromosomal variations can be regarded as normal chromosomes, which are not harmful to personal health and will not affect the fertility of offspring.

Chromosomal variation can be divided into many types, the common ones are heterochromatin length and position variation, as well as satellite and satellite stalk region variation. To know whether your chromosome is a variant chromosome, the easiest way is to see if there is a judgment of "chromosomal polymorphism" in the result description of our report. If your karyotype is "polymorphic", then you can rest assured that it is equivalent to a normal chromosome.

How to read the gender in chromosome karyotype analysis?

In the process of gamete formation in parents' reproduction, the two sex chromosomes separate from each other through meiosis. Males produce two types of sperm: sperm containing X chromosomes and sperm containing Y chromosomes. Females produce only one type of egg cell containing X chromosomes.

During fertilization, if an X-containing sperm cell combines with an egg cell, a fertilized egg with XX develops into a female; if a Y-containing sperm cell combines with an egg cell, a fertilized egg with XY develops into a male. This indicates that the gender of males and females is determined at the formation of the fertilized egg. As males can produce equal numbers of X and Y sperm, and their chances of combining with an egg cell are equal, the chances of having a boy or a girl are equal. The ratio of male to female in the entire population is roughly 1:1.