The genetic condition in human males characterized by the sex chromosome complement XXY is known as:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Turner's syndrome
• Down's syndrome
• Klinefelter's syndrome
• Patau syndrome
Correct Option: C  [ Klinefelter's syndrome ]

Remark: Klinefelter's syndrome is an aneuploidy (change in chromosome number) in males with the karyotype 47,XXY.

Which chromosomal disorder involves the absence of one X chromosome, resulting in the sex chromosome complement XO?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Down's syndrome
• Klinefelter's syndrome
• Turner's syndrome
• Triple X syndrome
Correct Option: C  [ Turner's syndrome ]

Remark: Turner's syndrome is an aneuploidy in females where one X chromosome is missing, leading to the karyotype 45,X.

Aneuploidy, which is a change in a subset of chromosome numbers, is primarily caused by which error during cell division?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Mutation
• Crossing over
• Non-disjunction
• Linkage
Correct Option: C  [ Non-disjunction ]

Remark: Aneuploidy (having an abnormal number of chromosomes, like trisomy or monosomy) is most often due to non-disjunction—the failure of homologous chromosomes or sister chromatids to separate during meiosis or mitosis.

What is the primary purpose of a pedigree analysis?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• To determine the exact gene sequence of an organism.
• To study the pattern of inheritance of a specific trait across generations in a family.
• To count the total number of chromosomes in a cell.
• To identify point mutations.
Correct Option: B  [ To study the pattern of inheritance of a specific trait across generations in a family. ]

Remark: Pedigree analysis uses standardized symbols to track a specific trait or disorder through multiple generations of a family, helping to suggest the mode of inheritance (e.g., autosomal dominant, X-linked recessive).

The total number of chromosomes in an individual with Down's syndrome is:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• 45
• 46
• 47
• 48
Correct Option: C  [ 47 ]

Remark: A normal human has 46 chromosomes (2n=46). Down's syndrome (Trisomy 21) means there is an extra copy of chromosome 21, resulting in 46+1=47 chromosomes.

Sex determination in human beings is based on which combination of chromosomes?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• XX in males, XY in females
• XY in males, XX in females
• XO in males, XX in females
• ZZ in males, ZW in females
Correct Option: B  [ XY in males, XX in females ]

Remark: Humans have an XX-XY system. Males are heterogametic (XY) and females are homogametic (XX). The male's sperm determines the sex of the offspring.

Which of the following is a symptom associated with Klinefelter's syndrome (47,XXY)?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Short stature and webbed neck
• Characteristic facial features (up-slanting eyes)
• Gynecomastia (development of breast tissue) and small testes
• Severe cognitive impairment
Correct Option: C  [ Gynecomastia and small testes ]

Remark: Males with Klinefelter's syndrome often exhibit reduced secondary sexual characteristics, infertility (small testes), and breast development (gynecomastia).

Which of the following is an example of an autosomal genetic disorder (mentioned or implied by the text's focus)?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Turner's syndrome
• Hemophilia
• Down's syndrome
• Klinefelter's syndrome
Correct Option: C  [ Down's syndrome ]

Remark: Down's syndrome (Trisomy 21) is a disorder of an autosome (non-sex chromosome). Turner's and Klinefelter's are sex-chromosomal disorders, and Hemophilia is X-linked.

Polyploidy is defined as a change in the entire set of chromosomes. In which group is polyploidy most commonly observed?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Humans
• Insects
• Plants
• Mammals
Correct Option: C  [ Plants ]

Remark: While polyploidy is lethal or causes severe issues in most animals, it is common and often advantageous in plants, leading to increased vigor and larger fruits/flowers.

Which of the following characteristics is typically associated with Turner's syndrome (45,X)?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Extreme height
• Fertile ovaries
• Underdeveloped ovaries and sterility
• Presence of Barr body
Correct Option: C  [ Underdeveloped ovaries and sterility ]

Remark: Turner's syndrome affects females, leading to rudimentary sexual development, including underdeveloped ovaries and consequent infertility.