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Nondisjunction

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers. Nondisjunction is common during anaphase I or anaphase II of meiosis. Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

X and Y Chromosomes

X and Y Chromosomes

Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A human female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...

The Ratio of X Chromosome to Autosomes

The Ratio of X Chromosome to Autosomes

In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...

Sex-linked Disorders

Sex-linked Disorders

Like autosomes, sex chromosomes contain a variety of genes necessary for normal body function. When a mutation in one of these genes results in biological deficits, the disorder is considered sex-linked.

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Exploring X Chromosomal Aberrations in Ovarian Cells by Using Fluorescence In Situ Hybridization

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Published on: April 7, 2023

[Pure 46,XY gonadal dysgenesis].

László Ságodi¹, Erzsébet Ladányi, Ákos Kiss

¹Borsod-Abaúj-Zemplén Megyei Kórház és Egyetemi Oktató Kórház Gyermekegészségügyi Központ, III. Csecsemő- és Gyermekosztály Miskolc Szentpéteri kapu 72. 3501 Miskolci Egyetem, Egészségügyi Kar Fizioterápiás Tanszék Miskolc. lsagodi@freemail.hu

|November 19, 2010

Summary

A rare case of Swyer syndrome (46,XY gonadal dysgenesis) in a 16-year-old female highlights the importance of karyotype analysis for primary amenorrhea. Early diagnosis and gonadectomy are crucial due to neoplasia risk.

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Area of Science:

Genetics
Endocrinology
Reproductive Medicine

Background:

Pure 46,XY gonadal dysgenesis, or Swyer syndrome, is a rare condition characterized by a 46,XY karyotype in a phenotypic female with primary amenorrhea and streak gonads.
Genetic mutations in testis differentiation pathways, including SRY and SF1, underlie this syndrome, though specific gene mutations are identified in a minority of cases.

Observation:

A 16-year-old phenotypic female presented with primary amenorrhea, Tanner I breast development, and Tanner II pubic hair.
Pelvic MRI revealed a hypoplastic uterus and bilateral streak gonads. Karyotype analysis confirmed a 46,XY karyotype.
Genetic analysis for SRY and SF1 mutations was negative, with elevated follicle-stimulating hormone and luteinizing hormone levels.

Findings:

Histological examination post-gonadectomy confirmed bilateral streak gonads.
Hormone replacement therapy initiated after gonadectomy led to the development of secondary sexual characteristics and menarche within 1.5 years.

Implications:

Karyotype analysis is essential for adolescent primary amenorrhea diagnosis.
Prophylactic bilateral gonadectomy is recommended in Swyer syndrome to mitigate the high risk of gonadal neoplasia.