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Related Concept Videos

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 I03:09

Meiosis I

Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of meiosis, where the genetic recombination of homologous chromosomes and the reduction of the ploidy level by half occurs.
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...
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...
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...
Oogenesis02:07

Oogenesis

In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...
Longitudinal Research02:20

Longitudinal Research

Sometimes we want to see how people change over time, as in studies of human development and lifespan. When we test the same group of individuals repeatedly over an extended period of time, we are conducting longitudinal research. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time. For example, we may survey a group of individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again...

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Related Experiment Video

Updated: May 29, 2026

In Vitro Modeling of Down Syndrome Neurogenesis Using Human-Induced Pluripotent Stem Cells
06:38

In Vitro Modeling of Down Syndrome Neurogenesis Using Human-Induced Pluripotent Stem Cells

Published on: March 7, 2025

Studies on down's syndrome and maternal age.

S K Subbegowda1, H S Narayanan, T S Padmashree

  • 1National Institute of Mental Health and Neuro Sciences, Bangalore - 560 029.

Indian Journal of Psychiatry
|September 20, 2011
PubMed
Summary

This study investigated 30 patients with Down syndrome, confirming Trisomy 21 in all cases. Notably, maternal age did not appear to be a significant factor, differing from findings in Western countries.

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Area of Science:

  • Genetics
  • Pediatrics
  • Clinical Medicine

Background:

  • Down syndrome, characterized by Trisomy 21, is a significant genetic disorder.
  • Maternal age is a well-established risk factor for Down syndrome in Western populations.

Purpose of the Study:

  • To investigate the clinical, genetic, and karyotyping details of patients with Down syndrome.
  • To explore the correlation between maternal age and Down syndrome in a specific cohort.

Main Methods:

  • Clinical examinations were performed on thirty patients diagnosed with Down syndrome.
  • Genetic and karyotyping analyses were conducted to confirm Trisomy 21.
  • Maternal age data was collected and analyzed for all participants.

Main Results:

  • All thirty patients presented with confirmed Trisomy 21.
  • Down syndrome cases were observed in mothers aged 15-35, a finding contrasting with Western data.
  • No specific correlation with maternal age was highlighted in this cohort.

Conclusions:

  • Trisomy 21 is the definitive genetic cause of Down syndrome in the studied population.
  • The observed lower maternal age association warrants further investigation and comparison with global data.