Problem 14 - Biology: The Unity and Diversity of Life

Question

Klinefelter syndrome (XXY) can be easily diagnosed by ____________. a. pedigree analysis c. karyotyping b. aneuploidy d. phenotypic treatment

Step-by-Step Solution

Answer

Klinefelter syndrome (XXY) can be easily diagnosed by karyotyping.

Step 1: Understanding Diagnosing Techniques

First, let's understand each of the options given for diagnosing Klinefelter syndrome. Pedigree analysis is a method used to determine the inheritance of traits through generations within a family but may not directly diagnose chromosomal abnormalities like Klinefelter syndrome. Aneuploidy refers to an abnormal number of chromosomes, which defines the condition but doesn't specify the diagnostic technique. Phenotypic treatment refers to treating the symptoms, not diagnosing the condition. Karyotyping is a laboratory procedure where the number and appearance of chromosomes in a cell are examined, which can directly confirm the presence of the extra X chromosome in Klinefelter syndrome.

Step 2: Eliminate Incorrect Options

Eliminate options that do not directly diagnose Klinefelter syndrome. Pedigree analysis (option a) and phenotypic treatment (option d) do not provide direct methods to confirm the presence of an extra chromosome. Similarly, aneuploidy (option b) is a term describing the condition but is not a diagnostic method itself.

Step 3: Identify the Correct Answer

Karyotyping (option c) is a direct method used to diagnose Klinefelter syndrome by allowing for the visualization of the chromosomal arrangement to identify the presence of an extra X chromosome, thus confirming XXY.

Key Concepts

Pedigree Analysis

Pedigree analysis is a valuable tool used in genetics to track the inheritance patterns of specific traits or diseases through generations in a family. By studying family history and constructing a pedigree chart, geneticists can understand how traits are passed down and deduce if they are dominant, recessive, or linked to a particular chromosome. Despite its usefulness in tracking hereditary disorders or predicting the risk of passing on genetic conditions, pedigree analysis does not provide a direct diagnosis for chromosomal abnormalities such as Klinefelter syndrome. Instead, it informs whether conditions may be inherited due to genes on specific chromosomes. In such analysis, symbols represent individuals, and lines connect family members, making it possible to visualize patterns of traits appearing across generations. However, to get a direct diagnosis of conditions like Klinefelter syndrome, other methods must be employed.

Karyotyping

Karyotyping is a powerful laboratory technique used to examine the number and structure of chromosomes within a cell. This procedure involves collecting cells, usually from a blood sample, and arresting them in metaphase where chromosomes are most visible. These chromosomes are then stained, photographed, and arranged according to size and shape creating a karyotype. This process is critical for diagnosing chromosomal abnormalities like Klinefelter syndrome, which is characterized by the presence of an additional X chromosome, leading to the XXY configuration. In individuals with Klinefelter syndrome, a karyotype will clearly display this extra chromosome, allowing for a definitive diagnosis. Karyotyping not only identifies Klinefelter syndrome but also other numerical chromosomal abnormalities such as Down syndrome (Trisomy 21). This makes it an indispensable tool in genetic diagnosis, relevant for understanding aneuploidy conditions generally.

Chromosomal Abnormalities

Chromosomal abnormalities arise when there is a deviation in the number or structure of chromosomes, leading to conditions that can affect development and health. There are two primary types: numerical and structural abnormalities. Numerical abnormalities, such as trisomy and monosomy, refer to changes in the number of chromosomes. For example, Klinefelter syndrome is a numerical chromosomal abnormality known as 47,XXY, where individuals have an extra X chromosome. Aneuploidy is the general term used to describe such numerical variation, which can result in conditions like Down syndrome, Turner syndrome, or Klinefelter syndrome. Structural abnormalities, on the other hand, involve changes in the actual structure of a chromosome, such as deletions, duplications, inversions, or translocations. Both types of abnormalities can result from mistakes during cell division or due to exposure to certain environmental factors or inherited conditions. Understanding these abnormalities helps in diagnosing, studying inheritance patterns, and developing potential treatments.