Abnormal Development - Genetic

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Chromosomes in trisomy 21

This page gives a general introduction to information about genetic abnormalities their relationship to age, ethnicity and prenatal testing. Use the listed links for more information about specific abnormalities. In developed countries with increasing maternal age comes the increased risk of age related genetic abnormalities, such as trisomy 21.

In order to detect some genetic abnormalities many countries offer genetic screening programs that include maternal serum screening (MSS, for detection of Down's syndrome and neural tube defects), embryonic and newborn screening (for phenylketonuria (PKU), hypothyroidism, cystic fibrosis and metabolic disorders).

In terms of maternal/paternal family history, some ethnic backgrounds have been shown to have disease-associated genetic variants, though most common genetic diseases are consistent across ethnic boundaries. For example: Caucasians of northern European ancestry and cystic fibrosis (CTFR gene), Mediterranean, Asian and Far Eastern ancestry with beta-thalassaemia.

Note that the development of in vitro fertilization techniques now allows cells from early stage blastocysts to be removed and genetically analysed prior to implantation. This has raised some ethical issues relating to what parameters will be in future used in blastocyst selection.

Genetic Links: Introduction | Genetic risk maternal age | Trisomy 21 | Trisomy 18 | Trisomy 13 | Trisomy X | Monosomy | Fragile X | Williams | Alagille | Philadelphia chromosome | Hydatidiform Mole | Prenatal Diagnosis | Neonatal Diagnosis | International Classification of Diseases | Molecular Development - Genetics | Cell Division - Meiosis | Cell Division - Mitosis
Abnormality Links: Introduction | Genetic | Environmental | Unknown | Teratogens | Cardiovascular | Coelomic Cavity | Endocrine | Gastrointestinal Tract | Genital | Head | Integumentary | Musculoskeletal | Limb | Neural | Neural Crest | Renal | Respiratory | Placenta | Sensory | Hearing | Vision | Twinning | Developmental Origins of Health and Disease | ICD-10

Some Recent Findings

Human idiogram
  • Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies[1] "Available evidence strongly supports the use of chromosomal microarray (CMA) in place of G-banded karyotyping as the first-tier cytogenetic diagnostic test for patients with developmental delay/intellectual disability (DD/ID), autism spectrum disorders (ASD), or multiple congenital anomalies (MCA). G-banded karyotype analysis should be reserved for patients with obvious chromosomal syndromes (e.g., Down syndrome), a family history of chromosomal rearrangement, or a history of multiple miscarriages."
  • Maternal genes and facial clefts in offspring: a comprehensive search for genetic associations in two population-based cleft studies from Scandinavia[2] "Except for FLNB, HIC1 and ZNF189, maternal genes did not appear to influence the risk of clefting in our data. This is consistent with recent epidemiological findings showing no apparent difference between mother-to-offspring and father-to-offspring recurrence of clefts in these two populations. It is likely that fetal genes make the major genetic contribution to clefting risk in these populations, but we cannot rule out the possibility that maternal genes can affect risk through interactions with specific teratogens or fetal genes."
  • Altered intra-nuclear organisation of heterochromatin and genes in ICF syndrome[3] "The ICF syndrome is a rare autosomal recessive disorder, the most common symptoms of which are immunodeficiency, facial anomalies and cytogenetic defects involving decondensation and instability of chromosome 1, 9 and 16 centromeric regions. ...DNA hypomethylation, previously reported to correlate with the decondensation of centromeric regions in metaphase described in these patients, appears also to correlate with the heterochromatin spatial configuration in interphase. "

Human Oocyte Aneuploidy

  • Frequency and distribution of chromosome abnormalities in human oocytes[4] "It was previously shown that more than half of the human oocytes obtained from IVF patients of advanced reproductive age are aneuploid, due to meiosis I and meiosis II errors. The present paper further confirms that 61.8% of the oocytes tested by fluorescent probes specific for chromosomes 13, 16, 18, 21 and 22 are abnormal, representing predominantly chromatid errors, which are the major source of aneuploidy in the resulting embryos. Almost half of the oocytes with meiosis I errors (49.3%) are prone to sequential meiosis II errors, which may lead to aneuploidy rescue in 30.8% of the cases. Half of the detected aneuploidies (49.8%) are of complex nature with involvement of two or more chromosomes, or the same chromosome in both meiotic divisions. The aneuploidy rates for individual chromosomes are different, with a higher prevalence of chromosome 21 and 22 errors. The origin of aneuploidy for the individual chromosomes is also not random, with chromosome 16 and 22 errors originating more frequently in meiosis II, and chromosome 18, 13 and 21 errors in meiosis I. There is an age dependence not only for the overall frequency of aneuploidies, but also for each chromosome error, aneuploidies originating from meiosis I, meiosis II, and both meiosis I and meiosis II errors, as well as for different types of aneuploidies. The data further suggest the practical relevance of oocyte aneuploidy testing for detection and avoidance from transfer of the embryos deriving from aneuploid oocytes, which should contribute significantly to the pregnancy outcomes of IVF patients of advanced reproduction age."

Links: Genetic risk maternal age | Trisomy 21 | Trisomy 18 | Trisomy 13 | Oocyte Development

Human Chromosomes

Human idiogram

Idiogram Chromosome Banding - The term refers to the light and dark pattern, seen after staining with a dye, of individual chromosomes identified in metaphase. It is only in meiosis and mitosis during metaphase that chromosomes can be easily identified, during the normal cell life (interphase) the chromosomes are unravelled and distributed within the nucleus in chromosome territories. A band is that part of a chromosome which is clearly distinguishable from nearby regions by appearing darker or brighter with one or more banding techniques.

Human Idiogram: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | X | Y
Genetic abnormality locations: 1-4 | 5-8 | 9-12 | 13-16 | 17-20 | 21-XY | sSMC
Inheritance Pattern images: Autosomal dominant inheritance | Autosomal recessive inheritance | X-Linked dominant (affected father) | X-Linked dominant (affected mother) | X-Linked recessive (affected father) | X-Linked recessive (carrier mother) | Mitochondrial genome inheritance | Codominant inheritance | Genogram symbols | Genetics
Links: Genetics | Abnormal Development - Genetic

Genetic Inheritance

The figures below show the pattern of inheritance of a range of genetic disorders. In addition to these patterns are the known effects of increased maternal age and the effects of genetic mutations in the embryo and newborn.

Inheritance Pattern images: Autosomal dominant inheritance | Autosomal recessive inheritance | X-Linked dominant (affected father) | X-Linked dominant (affected mother) | X-Linked recessive (affected father) | X-Linked recessive (carrier mother) | Mitochondrial genome inheritance | Codominant inheritance | Genogram symbols | Genetics

Genome-wide association study

The National Human Genome Research Institute (USA) lists publications as part of the genome-wide association study (GWAS) in an attempt to assay at least 100,000 single nucleotide polymorphisms (SNPs) in the initial stage.

Links: Genome-wide association study | National Human Genome Research Institute

Genetic Abnormality Topics


In humans, the most common trisomy is trisomy 21 or Down syndrome.

The term trisomy refers to the abnormal copy number of a specific chromosome, that is 3 copies instead of 2. The abnormality is identified by the chromosome that is present as 3 copies within the cell.

Science Student Projects 2011

The links below are to pages prepared as part of an undergraduate science student projects carried out in the Embryology course. Please note these are student submissions and may include inaccuracies in either description or understanding.

2011 Projects: Turner Syndrome | DiGeorge Syndrome | Klinefelter's Syndrome | Huntington's Disease | Fragile X Syndrome | Tetralogy of Fallot | Angelman Syndrome | Friedreich's Ataxia | Williams-Beuren Syndrome | Duchenne Muscular Dystrolphy | Cleft Palate and Lip


  1. David T Miller, Margaret P Adam, Swaroop Aradhya, Leslie G Biesecker, Arthur R Brothman, Nigel P Carter, Deanna M Church, John A Crolla, Evan E Eichler, Charles J Epstein, W Andrew Faucett, Lars Feuk, Jan M Friedman, Ada Hamosh, Laird Jackson, Erin B Kaminsky, Klaas Kok, Ian D Krantz, Robert M Kuhn, Charles Lee, James M Ostell, Carla Rosenberg, Stephen W Scherer, Nancy B Spinner, Dimitri J Stavropoulos, James H Tepperberg, Erik C Thorland, Joris R Vermeesch, Darrel J Waggoner, Michael S Watson, Christa Lese Martin, David H Ledbetter Consensus statement: chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. Am. J. Hum. Genet.: 2010, 86(5);749-64 PubMed 20466091 | DOI
  2. Astanand Jugessur, Min Shi, Håkon Kristian Gjessing, Rolv Terje Lie, Allen James Wilcox, Clarice Ring Weinberg, Kaare Christensen, Abee Lowman Boyles, Sandra Daack-Hirsch, Truc Trung Nguyen, Lene Christiansen, Andrew Carl Lidral, Jeffrey Clark Murray Maternal genes and facial clefts in offspring: a comprehensive search for genetic associations in two population-based cleft studies from Scandinavia. PLoS ONE: 2010, 5(7);e11493 PubMed 20634891
  3. Andrew Jefferson, Stefano Colella, Daniela Moralli, Natalie Wilson, Mohammed Yusuf, Giorgio Gimelli, Jiannis Ragoussis, Emanuela V Volpi Altered intra-nuclear organisation of heterochromatin and genes in ICF syndrome. PLoS ONE: 2010, 5(6);e11364 PubMed 20613881
  4. A Kuliev, J Cieslak, Y Verlinsky Frequency and distribution of chromosome abnormalities in human oocytes. Cytogenet. Genome Res.: 2005, 111(3-4);193-8 PubMed 16192694



Search Pubmed

Search Pubmed: genetic developmental abnormality


  • anaphase - (Greek, ana = up, again) Cell division term referring to the fourth mitotic stage, where the paired chromatids now separate and migrate to spindle poles. This is followed by telophase.
Mitosis Phases: prophase - prometaphase - metaphase - anaphase - telophase
  • anaphase B - Cell division term referring to the part of anaphase during which the poles of the mitotic spindle move apart. (More? Cell Division - Mitosis)
  • aneuploidy - Genetic term used to describe an abnormal number of chromosomes mainly (90%) due to chromosome malsegregation mechanisms in maternal meiosis I.
  • disomy - Genetic term referring to the presence of two chromosomes of a homologous pair in a cell, as in diploid. See chromosomal number genetic disorders uniparental disomy and aneuploidy. Humans have pairs usually formed by one chromosome from each parent.
  • meiosis I (MI) The first part of meiosis resulting in separation of homologous chromosomes, in humans producing two haploid cells (N chromosomes, 23), a reductional division.
Meiosis I: Prophase I - Metaphase I - Anaphase I - Telophase I
  • meiosis II - (MII) The second part of meiosis. In male human spermatogenesis, producing of four haploid cells (23 chromosomes, 1N) from the two haploid cells (23 chromosomes, 1N), each of the chromosomes consisting of two sister chromatids produced in meiosis I. In female human oogenesis, only a single haploid cell (23 chromosomes, 1N) is produced.
Meiosis II: Prophase II - Metaphase II - Anaphase II - Telophase II
  • prometaphase - (Greek, pro = before) Cell division term referring to the second mitotic stage, when the nuclear envelope breaks down into vesicles. Microtubules then extend from the centrosomes at the spindle poles (ends) and reach the chromosomes. This is followed by metaphase.
  • Philadelphia chromosome - (Philadelphia translocation) Genetic term referring to a chromosomal abnormality resulting from a reciprocal translocation between chromosome 9 and 22 (t(9;22)(q34;q11)). This is associated with the disease chronic myelogenous leukemia (CML).
  • prophase - (Greek, pro = before) Cell division term referring to the first mitotic stage, when the diffusely stained chromatin resolves into discrete chromosomes, each consisting of two chromatids joined together at the centromere.
  • telophase - Cell division term referring to the fifth mitotic stage, where the vesicles of the nuclear envelope reform around the daughter cells, the nucleoli reappear and the chromosomes unfold to allow gene expression to begin. This phase overlaps with cytokinesis, the division of the cell cytoplasm.
  • uniparental disomy - Genetic term referring to cells containing both copies of a homologous pair of chromosomes from one parent and none from the other parent.

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

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Cite this page: Hill, M.A. (2016) Embryology Abnormal Development - Genetic. Retrieved July 31, 2016, from https://embryology.med.unsw.edu.au/embryology/index.php/Abnormal_Development_-_Genetic

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© Dr Mark Hill 2016, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G