Question

Given below are two statements: Statement (I): Regression of offspring on mid parents as compared to on one parent yields lower precision. Statement (II): Heritability estimates based on the full sib families are less précised as compared to half sib families. In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

Precision is inversely proportional to standard error.
Both mid-parent regression and full-sib analyses reduce standard errors, thereby increasing the precision of heritability estimates compared to their counterparts.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Heritability (\( h^2 \)) can be estimated using parent-offspring regression or sib analyses.
Precision refers to the statistical standard error of the estimate.
A smaller standard error corresponds to higher precision.

Step 2: Detailed Explanation:
Let us analyze the statistical precision of both statements.
- Statement (I) compares single-parent and mid-parent regressions.
The regression of offspring on one parent estimates \( h^2 / 2 \), meaning \( h^2 = 2 \times b \).
The regression of offspring on the mid-parent (the average of both parents) directly estimates \( h^2 \), meaning \( h^2 = b \).
Since the mid-parent value is an average, its variance is halved (\( V_{\bar{P}} = \frac{1}{2} V_P \)).
This reduction in parental variance lowers the standard error of the regression coefficient.
Thus, mid-parent regression yields *higher* precision (smaller standard error) than single-parent regression, making Statement (I) incorrect.
- Statement (II) compares full-sib and half-sib family estimates.
Full-sibs share \( 50\% \) of their additive genetic variance, whereas half-sibs share only \( 25\% \).
Because the genetic relationship is stronger in full-sibs, the intraclass correlation is larger.
For a given sample size, a larger intraclass correlation coefficient results in a smaller standard error of the heritability estimate.
Thus, heritability estimates from full-sib families are *more* precise (have a lower standard error) than those from half-sib families, making Statement (II) incorrect.
Therefore, both statements are incorrect.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are incorrect, corresponding to option 2.