Question

The genotype XXY corresponds to: a. Klinefelter syndrome b. Turner syndrome c. Triplo-X d. Jacob syndrome

Short answer

The genotype XXY corresponds to Klinefelter syndrome.

Step-by-step solution

Understanding the genotype XXY

The given genotype XXY means that there are two X chromosomes and one Y chromosome present in the individual's genotype. This occurs when there is a nondisjunction event during the formation of sperm or egg, which causes an improper separation of sex chromosomes.

Identifying Klinefelter Syndrome

Klinefelter syndrome is a genetic disorder that affects males and occurs when they have an extra X chromosome, resulting in the genotype XXY. Males with this syndrome have a male phenotype (physical appearance), but often present mild signs of feminization, such as reduced facial and body hair, wider hips, and breast development. These individuals also tend to have lower testosterone levels, which can lead to infertility.

Identifying Turner Syndrome

Turner Syndrome is a genetic disorder that affects females who have only one X chromosome, resulting in the genotype XO. This syndrome results in a number of physical abnormalities including short stature, a webbed neck, and underdeveloped gonads. Females with Turner Syndrome are usually sterile.

Identifying Triplo-X Syndrome

Triplo-X Syndrome is a genetic disorder that affects females who have an extra X chromosome, resulting in the genotype XXX. These individuals usually have normal female appearances and development but may experience some developmental delays and learning difficulties.

Identifying Jacob Syndrome

Jacob Syndrome, also known as XYY Syndrome, is a genetic disorder that affects males who have an extra Y chromosome, resulting in the genotype XYY. These individuals are usually taller than average and may experience some developmental delays, learning difficulties, and behavioral issues, but they generally have a normal male appearance and are fertile.

Matching the genotype to the syndrome

From our analysis of each syndrome, it is clear that the genotype XXY corresponds to Klinefelter Syndrome, as it is the only one among the options that has this specific chromosomal combination. So, the correct answer is: a. Klinefelter syndrome

Key concepts

genotype XXY

Understanding the genetic makeup of an individual involves looking at their chromosomes, which carry their genetic information. When we mention the term genotype XXY, we are referring to a specific chromosomal composition. This genotype includes two X chromosomes and one Y chromosome. Normally, males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).
Typically, this unusual combination arises due to an event called nondisjunction, which occurs when sex chromosomes don't separate properly during the formation of reproductive cells - sperm or eggs. As a result, a child is born with an extra X chromosome. The phenotype, or physical expression of this genotype, can vary, but commonly, individuals with XXY experience some degree of physical and developmental differences compared to the typical male XY genotype.
Understanding that the XXY genotype leads to distinct physical and developmental features is crucial when studying genetic disorders, especially in the context of Klinefelter syndrome, which is characterized by this specific chromosomal arrangement.

genetic disorders

A genetic disorder is a disease that is caused by abnormalities in an individual's DNA, often through mutations or variations in chromosomes. These can be inherited from parents or occur spontaneously. Conditions like Klinefelter syndrome, Turner syndrome, and others mentioned in the exercise are prime examples of such disorders.
When considering genetic disorders, it's important to understand that they can vary widely in their presentation and severity. Some, like Klinefelter syndrome, may present with subtle symptoms and often go undiagnosed until later in life, whereas others might have a more immediate impact on an individual’s health and development.

Educational Note:

• Students should be aware that not all genetic disorders are detectable at birth.
• Genetic counseling can often provide valuable insights into these conditions.
• Advancements in genetic testing have improved our ability to diagnose and manage these disorders.

Recognizing the diverse nature of genetic disorders and their genetic bases is essential for students learning about genetics. It emphasizes the importance of precision and care when studying an individual's chromosomes to understand their health and development.

sex chromosomes

Sex chromosomes are a pair of chromosomes that determine an individual's sex and related characteristics. In humans, these are referred to as the X and Y chromosomes, with the typical male having one X and one Y chromosome (XY) and the typical female having two X chromosomes (XX).
These chromosomes are responsible for the development of sexual anatomy and secondary sexual characteristics. It's the presence or absence of certain genes on these chromosomes that guide the development of a fetus into a male or a female. In the case of some genetic disorders, the normal pattern of sex chromosomes is disrupted, resulting in atypical development.
The study of sex chromosomes is fundamental in genetics, as they carry significant determinants of our biological sex and can uncover the potential for various genetic disorders. With this knowledge, students gain a deeper appreciation for the complexity of genetics and how it pertains to human diversity and medicine.