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Related Concept Videos

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

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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.
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...
Meiosis I03:09

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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.
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Using a Comparative Species Approach to Investigate the Neurobiology of Paternal Responses
07:59

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Published on: September 19, 2011

Parental age difference and offspring count in humans.

Martin Fieder1, Susanne Huber

  • 1Department of Anthropology, University of Vienna, Aethanstrasse 14, 1090 Vienna, Austria. martin.fieder@univie.ac.at

Biology Letters
|August 30, 2007
PubMed
Summary

Men and women show partner age preferences that enhance reproductive fitness. Optimal offspring count is achieved with partners younger for men and older for women, suggesting an evolved trait.

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Published on: October 13, 2018

Area of Science:

  • Evolutionary biology
  • Human reproductive behavior
  • Social psychology

Background:

  • Cross-cultural observations indicate consistent age preferences in mate selection.
  • Men typically prefer younger partners, while women tend to prefer older partners.
  • The evolutionary basis and fitness consequences of these age preferences remain under investigation.

Purpose of the Study:

  • To investigate the association between age differences in partners and reproductive success (offspring count).
  • To determine if specific age differentials correlate with maximum offspring production in men and women.
  • To examine shifts in partner age preference following relationship separation.

Main Methods:

  • Analysis of a large dataset of approximately 10,000 post-reproductive Swedish individuals.
  • Focus on individuals who maintained the same partner from their first to last child.
  • Statistical examination of the relationship between age differences and total offspring count.

Main Results:

  • Maximum offspring count in men was observed when their partner was approximately 6 years younger.
  • Maximum offspring count in women was observed when their partner was approximately 4 years older.
  • Post-separation partner shifts indicated a trend towards younger partners for both sexes, though women's new partners remained older than themselves.

Conclusions:

  • Partner age preferences appear to confer significant fitness benefits, maximizing offspring count for both men and women.
  • These findings support the hypothesis that age-based mate selection strategies are evolutionarily acquired traits.
  • The observed preferences likely reflect adaptive mechanisms promoting reproductive success across different sexes.