Karyotyping is a technique that is most useful for diagnosing which type of genetic disorder?

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

• Single-gene (Mendelian) disorders
• Mitochondrial disorders
• Chromosomal disorders (Aneuploidy)
• Point mutations
Correct Option: C  [ Chromosomal disorders (Aneuploidy) ]

Remark: Karyotyping involves arranging the chromosomes of a cell based on size and structure, allowing for the easy detection of abnormal chromosome numbers (aneuploidy) or structural changes.

If the mother's blood group is B (heterozygous I^Bi) and the father's blood group is A (heterozygous I^Ai), what is the probability of having an offspring with Blood Group AB?

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

• 1/4
• 1/2
• 3/4
• 0
Correct Option: A  [ 1/4 ]

Remark: The cross I^Ai × I^Bi yields: I^AI^B (AB), I^Ai (A), I^Bi (B), and i i (O). The probability of I^AI^B (AB) is 1 out of 4, or 1/4.

A child with Turner's syndrome has how many autosomes?

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

• 44
• 45
• 46
• 23
Correct Option: A  [ 44 ]

Remark: A normal human has 22 pairs of autosomes (44 total) and one pair of sex chromosomes (XX or XY). Turner's syndrome is 45,X, meaning 44 autosomes and only one X sex chromosome.

What is the full karyotype of a male with Klinefelter’s syndrome?

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

• 47, XY, +21
• 45, X
• 47, XXY
• 46, XX
Correct Option: C  [ 47, XXY ]

Remark: Klinefelter’s syndrome is characterized by 47 chromosomes, including an extra X in a male: 47,XXY.

The two autosomal genetic disorders mentioned in the text are the result of:

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

• Gene mutation
• Point mutation
• Aneuploidy
• Linkage
Correct Option: C  [ Aneuploidy ]

Remark: The text specifically mentions Down’s syndrome (Trisomy 21), Turner’s syndrome (XO), and Klinefelter’s syndrome (XXY) as being due to change in a subset of chromosome number (aneuploidy). Down's is the autosomal example of aneuploidy among the listed disorders.

Which stage of meiosis is most prone to the non-disjunction event that causes aneuploidy?

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

• Prophase I or Prophase II
• Metaphase I or Metaphase II
• Anaphase I or Anaphase II
• Telophase I or Telophase II
Correct Option: C  [ Anaphase I or Anaphase II ]

Remark: Non-disjunction is the failure of homologous chromosomes to separate during Anaphase I, or the failure of sister chromatids to separate during Anaphase II.

In the study of pedigree analysis, a square symbol usually represents:

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

• A female
• An affected individual
• A male
• A deceased individual
Correct Option: C  [ A male ]

Remark: In standard pedigree charts, circles represent females, and squares represent males.

The total chromosome count for an individual with Turner's syndrome is:

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

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

Remark: Turner's syndrome is 45,X, meaning there is one fewer sex chromosome than normal (46 − 1 = 45).

If an autosomal recessive disorder is tracked via pedigree, how would two unaffected parents transmit the trait to their offspring?

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

• Both parents must be homozygous dominant.
• Both parents must be heterozygous carriers.
• One parent is homozygous dominant, the other is heterozygous.
• Both parents must have the trait.
Correct Option: B  [ Both parents must be heterozygous carriers. ]

Remark: In an autosomal recessive disorder, unaffected parents can only have an affected child if both are heterozygous carriers (Aa × Aa), resulting in a 25% chance of an affected homozygous recessive (aa) child.

What is a 'point mutation'?

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

• A change in the entire set of chromosomes.
• A deletion or insertion of a large segment of DNA.
• A change in a single base pair of DNA.
• A mutation that affects multiple genes simultaneously.
Correct Option: C  [ A change in a single base pair of DNA ]

Remark: A point mutation is a small-scale mutation involving a change in just one base pair in the DNA sequence.