Test: Chromosomal Theory of Inheritance - Grade 12 MCQ

The assertion accurately states that in pea plants, the allele for yellow seed color is dominant over the allele for green seed color. The reason is also true and correctly explains the assertion because plants with yellow seeds can have either a homozygous dominant (YY) or heterozygous (Yy) genotype, which is how dominance works in Mendelian genetics.

Theodore Boveri and Walter Sutton had unraveled the mechanisms underlying the chromosome movement during cell division. These movements were correlated with Mende’s laws.

Solution:

1. Option A: They can be cultured on a simple nutrient medium.
   This statement is correct. Drosophila melanogaster can be cultured on a simple medium, making them easy to maintain and inexpensive for laboratory studies.

2. Option B: Their life cycle is completed in approximately 10–14 days.
   This statement is correct. Drosophila have a rapid life cycle of about 10 to 14 days, allowing researchers to study multiple generations quickly.

3. Option C: A single pair of flies can produce thousands of offspring in one mating.
   This statement is correct. A single mating pair can produce hundreds to thousands of offspring over several generations, which is advantageous for genetic analysis.

4. Option D: Sexual dimorphism is absent, making sex determination difficult.
   This statement is incorrect. Drosophila exhibit clear sexual dimorphism. Males are smaller and have distinctive features like sex combs on their forelegs, while females have larger abdomens. This makes sex determination relatively easy, not difficult.

Chromosomes means colored bodies/objects. The staining procedures allowed biologists to visualize the nucleus and chromosomes during the process of cell division.

The image shows two different possibilities for how chromosomes can align and separate during anaphase I and anaphase II of meiosis, leading to genetic variation in the gametes. This process is known as independent assortment, where different pairs of chromosomes segregate independently from each other.

Mendel’s work was laid in papers before people could recognize it after 1900. This was achieved by the rediscovery of his work by three scientists: de Vries, Correns, and Tschermark.

Mendel’s work suggested the existence of stable and discrete factors. This was completely shocking for the contemporary scientific world. A major drawback that lied was the inability to discover the factors and prove their existence.