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Related Concept Videos

Karyotyping01:17

Karyotyping

Overview
Karyotyping01:17

Karyotyping

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Nondisjunction01:21

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...
Nondisjunction01:29

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.
Meiosis vs. Mitosis02:57

Meiosis vs. Mitosis

Cell division is necessary for growth and reproduction in organisms. Mitosis aids cell growth and development by dividing somatic cells. In contrast, meiosis causes the division of germ cells and plays an essential role in sexual reproduction. Due to their unique functional requirements, mitosis and meiosis differ from each other in multiple aspects.
Before the start of mitosis and meiosis I, the cell synthesizes DNA, resulting in two homologous copies of each chromosome. DNA synthesis is...
Meiosis I01:49

Meiosis I

Meiosis is a carefully orchestrated set of cell divisions, the goal of which—in humans—is to produce haploid sperm or eggs, each containing half the number of chromosomes present in somatic cells elsewhere in the body. Meiosis I is the first such division, and involves several key steps, among them: condensation of replicated chromosomes in diploid cells; the pairing of homologous chromosomes and their exchange of information; and finally, the separation of homologous chromosomes by a...

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Related Experiment Video

Updated: May 23, 2026

Spectral Karyotyping to Study Chromosome Abnormalities in Humans and Mice with Polycystic Kidney Disease
12:47

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Association between increased yolk sac diameter and abnormal karyotypes.

Ksenija Gersak1, Alenka Veble, Zuber D Mulla

  • 1Department of Obstetrics and Gynecology, University Medical Center Ljubljana, Slajmerjeva 3, 1000 Ljubljana, Slovenia. ksenija.gersak@mf.uni-lj.si

Journal of Perinatal Medicine
|April 17, 2012
PubMed
Summary

An enlarged yolk sac (≥6 mm) in early pregnancy is often linked to abnormal karyotypes, but can also occur in viable pregnancies. Further ultrasound assessment is recommended for enlarged yolk sacs with normal karyotypes.

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Area of Science:

  • Maternal-Fetal Medicine
  • Prenatal Diagnostics
  • Genetics

Background:

  • The yolk sac is a crucial early pregnancy structure.
  • An enlarged yolk sac diameter has been anecdotally associated with adverse pregnancy outcomes.

Purpose of the Study:

  • To investigate the association between an increased yolk sac diameter and abnormal fetal karyotype.
  • To determine the predictive value of yolk sac size for pregnancy viability and chromosomal abnormalities.

Main Methods:

  • Retrospective analysis of 42 pregnancies (6-12 weeks gestation) with yolk sac diameter ≥6 mm.
  • Transvaginal ultrasound assessment correlated with chorionic villi karyotype results.
  • Statistical analysis using Fisher's exact test and logistic regression.

Main Results:

  • Chromosome abnormalities were detected in 76.2% of cases.
  • A significant association was found between karyotype and missed abortion (P=0.001).
  • No viable pregnancies with yolk sac diameter ≥8 mm had a normal karyotype; Trisomy 15/16 strongly associated with missed abortion.

Conclusions:

  • An enlarged yolk sac (≥6 mm) can be observed in viable pregnancies.
  • Patients with enlarged yolk sacs and normal karyotypes require detailed second and third-trimester ultrasound surveillance.
  • Yolk sac size is a potential early indicator, but not definitive, of fetal karyotype status.