In the following figure, two ways of pairing of two homologous pairs of chromosomes are shown. Which of the following phenomena is expressed?
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Independent assortment occurs because the orientation of homologous pairs at the metaphase plate is random.
This process, along with crossing over, is a primary source of genetic variation in sexually reproducing organisms.
Step 1: Understanding the Concept:
The question refers to the behavior of chromosomes during Meiosis I, specifically during Metaphase I.
The law illustrated here is the Law of Independent Assortment, which states that different pairs of alleles (on different chromosomes) segregate independently of one another during gamete formation. Step 2: Detailed Explanation:
In the provided figure, "Possibility 1" and "Possibility 2" represent the random alignment of homologous chromosome pairs on the metaphase plate.
In Possibility 1, one alignment leads to specific combinations in the gametes (Combination 1 and 2).
In Possibility 2, a different alignment of the same chromosome pairs leads to different combinations (Combination 3 and 4).
Since the orientation of one bivalent is independent of the orientation of other bivalents, all types of gametic combinations are produced with equal frequency.
This random distribution of maternal and paternal chromosomes into gametes is the physical basis of Mendel's Law of Independent Assortment.
Linkage (Option A) would show genes staying together, which contradicts the "different combinations" shown in the figure. Step 3: Final Answer:
The diagram represents the independent assortment of chromosomes, which leads to genetic variation in gametes.
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