MAHARASHTRA-CLASS-XII SERIES Biology
Principles Of Inheritance And Variation
2 previous year questions.
Volume: 2 Ques
Yield: Medium
High-Yield Trend
2
2025 Chapter Questions 2 MCQs
01
PYQ 2025
medium
biology ID: maharash
What are chromosomal disorders? Describe Turner's syndrome and Klinefelter's syndrome.
Official Solution
Correct Option: (1)
Chromosomal disorders are genetic conditions caused by an abnormality in the number or structure of an individual's chromosomes. These abnormalities, known as chromosomal aberrations, arise from errors during gamete formation (meiosis), such as the failure of chromosomes to separate properly (non-disjunction). This results in a zygote with an abnormal number of chromosomes (aneuploidy) or structurally altered chromosomes, leading to a range of physical and developmental problems. Turner's Syndrome:
Cause: It is a chromosomal disorder caused by the absence of one of the X chromosomes in females. It is a monosomy of the sex chromosome, resulting in a karyotype of 45, XO instead of the normal 46, XX.
Symptoms: Individuals with Turner's syndrome are females with the following characteristics:
They are sterile because their ovaries are rudimentary and non-functional.
They have a short stature.
Physical features often include a broad, "shield-like" chest with widely spaced nipples, a webbed neck, and a low hairline at the back of the neck.
They lack secondary sexual characteristics at puberty.
Intelligence is generally normal, though some may have learning difficulties, particularly with spatial visualization.
Klinefelter's Syndrome:
Cause: This disorder is caused by the presence of an extra X chromosome in males. It is a trisomy of the sex chromosome, resulting in a karyotype of 47, XXY instead of the normal 46, XY.
Symptoms: Individuals with Klinefelter's syndrome are males who may exhibit the following characteristics:
They are sterile due to underdeveloped, small testes (testicular atrophy) and no sperm production (azoospermia).
They are often tall with disproportionately long arms and legs.
They have overall masculine development but also show some feminine characteristics, most notably the development of breast tissue (gynaecomastia).
They have sparse body and facial hair.
Testosterone levels are low, and they may have learning disabilities or delayed speech development.
Cause: It is a chromosomal disorder caused by the absence of one of the X chromosomes in females. It is a monosomy of the sex chromosome, resulting in a karyotype of 45, XO instead of the normal 46, XX.
Symptoms: Individuals with Turner's syndrome are females with the following characteristics:
They are sterile because their ovaries are rudimentary and non-functional.
They have a short stature.
Physical features often include a broad, "shield-like" chest with widely spaced nipples, a webbed neck, and a low hairline at the back of the neck.
They lack secondary sexual characteristics at puberty.
Intelligence is generally normal, though some may have learning difficulties, particularly with spatial visualization.
Klinefelter's Syndrome:
Cause: This disorder is caused by the presence of an extra X chromosome in males. It is a trisomy of the sex chromosome, resulting in a karyotype of 47, XXY instead of the normal 46, XY.
Symptoms: Individuals with Klinefelter's syndrome are males who may exhibit the following characteristics:
They are sterile due to underdeveloped, small testes (testicular atrophy) and no sperm production (azoospermia).
They are often tall with disproportionately long arms and legs.
They have overall masculine development but also show some feminine characteristics, most notably the development of breast tissue (gynaecomastia).
They have sparse body and facial hair.
Testosterone levels are low, and they may have learning disabilities or delayed speech development.
02
PYQ 2025
medium
biology ID: maharash
What are the reasons for the success of Mendel?
Official Solution
Correct Option: (1)
Gregor Mendel's Success in Discovering the Principles of Inheritance
- Choice of experimental material: Mendel chose the pea plant (Pisum sativum) as his experimental material. It was ideal because it is easy to cultivate, has a short life cycle, and produces many offspring.
- Selection of contrasting characters: He studied seven pairs of clearly distinguishable traits, such as:
- Tall vs. Dwarf plants
- Round vs. Wrinkled seeds
- Yellow vs. Green seed color
- Violet vs. White flowers
- Controlled pollination: Although pea plants are naturally self-pollinating, Mendel performed manual cross-pollination. To prevent accidental pollination, he carried out emasculation (removal of anthers).
- Quantitative approach: Mendel was the first to apply statistical and mathematical methods in biology. He analyzed ratios and probabilities, and kept accurate, detailed records of his experiments.
- Studying one character at a time: He initially focused on the inheritance of a single trait (monohybrid cross), before moving on to study two traits simultaneously (dihybrid cross).
- Careful experimentation: He began with pure-breeding parent plants and studied inheritance across several generations ( , , and ) to establish clear patterns.