Individuals with karyotype of 44+XXY having overall masculine development with few feminine development like Gynaecomastia has ________ chromosomal disorder.
Klinefelter's Syndrome
Understanding Chromosomal Disorders: The 44+XXY Karyotype
The question describes an individual with a specific karyotype, 44+XXY, exhibiting overall masculine development along with some feminine traits like Gynaecomastia. We need to identify the chromosomal disorder associated with these characteristics.
Analyzing the Karyotype: 44+XXY
A normal human karyotype has 46 chromosomes: 44 autosomes and 2 sex chromosomes. For males, this is typically 44+XY, and for females, it's 44+XX. The given karyotype, 44+XXY, means the individual has 44 autosomes and 3 sex chromosomes (XXY), totaling 44 + 3 = 47 chromosomes. This presence of an extra X chromosome in a male (who also has a Y chromosome) is a key indicator of a specific genetic condition.
Let's examine the options provided in the context of this karyotype and the described symptoms:
- Klinefelter's Syndrome: This syndrome is a genetic condition resulting from an extra X chromosome in males. The most common karyotype is 47, XXY, which is equivalent to 44 autosomes + XXY sex chromosomes. Individuals with Klinefelter's Syndrome are typically male but may present with features like reduced fertility, smaller testes, taller stature, and notably, gynecomastia (enlargement of male breast tissue), fitting the description in the question.
- Turner's Syndrome: This syndrome affects females and results from a missing or incomplete X chromosome. The typical karyotype is 45, X (44 autosomes + one X chromosome). Symptoms include short stature, infertility, and other developmental issues, which are different from the masculine development described.
- Down's Syndrome: This syndrome is caused by an extra copy of chromosome 21 (Trisomy 21). It affects autosomes, not sex chromosomes. The karyotype is typically 47, XX, +21 or 47, XY, +21. Symptoms include intellectual disability and specific facial and physical features, unrelated to the XXY karyotype or the combination of masculine traits and gynecomastia.
- Acquired Immuno Deficiency Syndrome (AIDS): This is a disease caused by the Human Immunodeficiency Virus (HIV). It affects the immune system and is not a chromosomal disorder at all.
Identifying the Correct Chromosomal Disorder
Based on the characteristic karyotype (44+XXY, or 47, XXY) and the description of masculine development with feminine features like Gynaecomastia, the disorder that matches these details is Klinefelter's Syndrome.
| Disorder | Typical Karyotype | Key Characteristics |
|---|---|---|
| Klinefelter's Syndrome | 47, XXY (or 44+XXY) | Males, masculine development, infertility, sometimes taller, gynecomastia, learning disabilities. |
| Turner's Syndrome | 45, X (or 44+X) | Females, short stature, infertility, webbed neck, heart defects. |
| Down's Syndrome | 47, +21 (Trisomy 21) | Intellectual disability, distinctive facial features, heart defects, developmental delays. |
| AIDS | N/A (Viral disease) | Immune system failure, opportunistic infections. |
Therefore, the condition described, with a karyotype of 44+XXY leading to masculine development and Gynaecomastia, is Klinefelter's Syndrome.
Revision Table: Comparing Chromosomal Disorders
| Disorder | Cause | Chromosomal Abnormality | Affected Sex | Key Symptoms (Selected) |
|---|---|---|---|---|
| Klinefelter's Syndrome | Non-disjunction during gamete formation | Extra X chromosome (47, XXY) | Males | Gynecomastia, infertility, tall stature, small testes |
| Turner's Syndrome | Monosomy of X chromosome | Missing X chromosome (45, X) | Females | Short stature, webbed neck, ovarian failure |
| Down's Syndrome | Trisomy of chromosome 21 | Extra copy of chromosome 21 (47, +21) | Both | Intellectual disability, characteristic facial features, heart defects |
Additional Information on Genetic and Chromosomal Disorders
Chromosomal disorders result from changes in the number or structure of chromosomes. These changes can occur spontaneously during the formation of egg or sperm cells (gametes) or during early embryonic development.
- Aneuploidy: This refers to the presence of an abnormal number of chromosomes. Having an extra chromosome is called trisomy (e.g., Trisomy 21 in Down's Syndrome, Trisomy XXY in Klinefelter's Syndrome), while having a missing chromosome is called monosomy (e.g., Monosomy X in Turner's Syndrome).
- Sex Chromosome Aneuploidies: These involve the X or Y chromosomes. Klinefelter's Syndrome (XXY), Turner's Syndrome (X), Triple X Syndrome (XXX), and XYY Syndrome are examples. These often affect sexual development and fertility, as sex chromosomes carry genes crucial for these processes.
- Autosomal Aneuploidies: These involve the non-sex chromosomes (autosomes). Trisomy 21 (Down's), Trisomy 18 (Edwards), and Trisomy 13 (Patau) are examples. These often result in more severe physical and intellectual disabilities compared to sex chromosome aneuploidies.
- Non-disjunction: This is the most common cause of aneuploidy. It occurs when homologous chromosomes or sister chromatids fail to separate properly during meiosis (gamete formation) or mitosis (cell division). This leads to gametes or cells with an abnormal number of chromosomes.
Understanding the specific karyotype is essential for diagnosing these genetic conditions. The karyotype analysis involves examining the number and structure of an individual's chromosomes, usually from a blood sample.
Important Questions from Inheritance and Disorders
Given below are two statements:
Statement I: Phenylketonuria is an example of Pleiotropy
Statement II: Affected individuals lack an enzyme which converts phenylalanine into tyrosine
In the light of the above statements, choose the most appropriate answer from the options given below:
The reason for deviation from Mendel's dihybrid cross in T.H. Morgan's experiment is ________.
Sutton united the knowledge of chromosomal segregation with Mendelian principles and called it the _______.
