Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Mendel’s law of Independent assortment does not hold goods for the genes that are located closely on the same chromosome.
Reason (R): Closely located genes assort independently.
Answer from the options given below:
Assertion (A): Mendel’s law of Independent assortment does not hold goods for the genes that are located closely on the same chromosome.
Reason (R): Closely located genes assort independently.
Answer from the options given below:
- Both (A) and (R) are correct and (R) is the correct explanation of (A)
- Both (A) and (R) are correct but (R) is not the correct explanation of (A)
- (A) is correct but (R) is not correct
- (A) is not correct but (R) is correct
The Correct Option is C
Solution and Explanation
Mendel's law of Independent Assortment states that genes located on different chromosomes are inherited independently of each other. However, this law does not fully apply to genes that are located closely on the same chromosome, as these genes are likely to be inherited together due to their physical proximity. This concept is known as genetic linkage, which can cause linked genes to be inherited together, thereby deviating from independent assortment. In the given assertion and reason:
Assertion (A): Mendel’s law of Independent assortment does not hold good for the genes that are located closely on the same chromosome. This statement is true because linkage affects the inheritance pattern of closely located genes on a chromosome.
Reason (R): Closely located genes assort independently. This statement is incorrect because closely located genes are often inherited together due to linkage, which contradicts the concept of independent assortment.
Therefore, the correct response is: (A) is correct but (R) is not correct.
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Concepts Used:
Chromosomal Theory of Inheritance
Chromosomal theory: Linkage and Genetic Recombination
If two genes were present on the same chromosome, the chances of getting a parental combination were much higher in the next generation in comparison to the non-parental combination. This physical association of genes was termed ‘linkage’. The description of the non-parental gene combinations in a dihybrid cross is termed ‘genetic recombination'. After the discovery of linked genes, the frequency of linked genes also influenced the appearance of traits in the next generation.
Observations of Chromosomal Theory of Inheritance:
- During the cell division-meiosis process, the pairs of homologous chromosomes move as discrete structures, which are independent of other pairs of chromosomes.
- From each homologous pair, there is a random distribution of chromosomes into the pre-gametes.
- Each parent synthesizes gametes, which add up to only half of their chromosomal complement.
- Even though female (egg) and male (sperm) gametes differ in morphology and size, they have the same number of chromosomes, submitting equal genetic contributions from each parent.
- The gametic chromosomes fuse during the process of fertilization to produce offspring with the same number of a chromosome as their parents.
Read More: Chromosomal Theory of Inheritance