Genetics in obstetrics and gynecology / Joe Leigh Simpson [and others].

Date:
[1982], ©1982
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Genetics in obstetrics and gynecology / Joe Leigh Simpson [and others]. Source: Wellcome Collection.

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    6 / GENETICS IN OBSTETRICS AND GYNECOLOGY Ш' 4 « im é I « ^ яг i Mé té И St 15 Ш m Sa ' ^ w ^ ^ V Pi f» 8 10 t f • ff II m f' Д*я » Г •• •» 12 i^Míi t i • I à й 13 14 15 16 17 18 0 • * I « • 19 20 21 22 X У Figure 1-3. Metaphase figure and karyotype of a normal male (46,XY) (G-banding technique). females, XY in males) (Figs. 1-3 and 1-4). The chromosome number is different in most other mammals. The aggregation of many genes in a limited number of chromosomes facilitates the ability of parental cells to transmit identical genetic information to daughter cells (mitosis), and to reduce their chromosome number by half (meiosis) so that each gamete contributes a haploid (n) number of chromosomes to the diploid (2n) zygote. (In humans n = 23). Errors of meiosis and mitosis lead to abnormal differentiation. Chromosomal analyses are usually performed on peripheral blood (lym¬ phocytes) or fibroblasts cultured from skin, gonads, or amniotic fluid cells. Cells are grown in nutrient media to which fetal calf serum and antibiotics are usually added. After a period of growth appropriate for a given tissue (48-72 hours for blood, 2—4 weeks for skin or amniotic fluid fibroblasts), cells are prepared for chromosomal analysis by the sequential addition of (1) colchicine (or desoxymethylcolchine); (2) a hypotonic solution that causes cells to swell; (3) an acetic acid-methanol fixative; and (4) a dye to enhance chromosome visibility. Other procedures may be used to produce horizontal banding patterns that allow a given pair of chromosomes to be distinguished from all others.