chromosomes
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Variations in chromosomal number include euploidy, which is the usual number of chromosomes, polyploidy which is three or more complete sets of chromosomes, and aneuploidy which is an additional or missing individual chromosome. Aneuploidy in humans can result in syndromes like Trisomy 13, Down Syndrome, Turner Syndrome, and Klinefelter Syndrome, which are characterized by developmental delays, physical abnormalities, and infertility.
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chromosomes
- 2. Variations in Chromosomal Number Euploidy – the usual number and sets of chromosomes Polyploidy – the presence of three or more complete sets of chromosomes Aneuploidy – the presence of additional chromosomes or missing individual chromosomes
- 3. Aneuploidy When aneuploidy occurs in humans, syndromes can result. Examples include the following: 1. Trisomy 13 2. Down Syndrome 3. Turner Syndrome 4. Klinefelter Syndrome
- 4. TRISOMY 13 Chromosomal Variation – Trisomy 13 (three copies of chromosome 13) Head and facial malformations Malformations of the hands and feet Skeletal malformations Kidney malformations Structural heart defects Early death DOWN SYNDROME Chromosomal Variation – Trisomy 21 (three copies of chromosome 21) Low muscle tone. Head and facial malformations. Abnormalities of the extremities. Developmental delays Heart malformations.
- 5. TURNER SYNDROME Monosomy of sex chromosome (only one X chromosome present) Short stature Lack of ovarian development Neck abnormalities Skeletal disorders KLINEFELTER SYNDROME Trisomy of sex chromosome – XXY (An additional X chromosomeTall in males) Sexually underdeveloped Infertility Sparse facial and body hair Developmental delays in males)
- 6. TURNER SYNDROME Monosomy of sex chromosome (only one X chromosome present) Short stature Lack of ovarian development Neck abnormalities Skeletal disorders KLINEFELTER SYNDROME Trisomy of sex chromosome – XXY (An additional X chromosomeTall in males) Sexually underdeveloped Infertility Sparse facial and body hair Developmental delays in males)
Editor's Notes
- Euploidy is the presence of the usual number of chromosomes in a cell. In the case of humans, there are generally two sets of 23 chromosomes or 46 total chromosomes in cells. However, in variations of chromosomal number, there can be differences. For example, polyploidy is the presence of three or more complete sets of chromosomes in a cell. Another example of a chromosomal alteration is aneuploidy, the presence of additional chromosomes or missing individual chromosome. (1)
- It is possible for babies with monosomy or trisomy to survive. In many cases, there are certain characteristics associated with aneuploidy, depending on which chromosome(s) are affected and the severity of the affected chromosome(s). Characteristics also vary depending on the number of cells that have the chromosomal variation. If very few cells have the variation, severity will be minimal. If most have the variation, severity will be much greater. (3) When an individual has a particular karyotype as well as specified characteristics, their condition is defined as a syndrome. Some examples of aneuploidy associated syndromes include Trisomy 13, Trisomy 18, Down Syndrome, Turner syndrome, Klinefelter Syndrome, and XYY syndrome. The remainder of the presentation will discuss these syndromes and their features. (1)