2.
Which one of the following would produce the highest variability of gametes if the alleles
assorted independently?
a. Yy PP Tt Rr
b. Yy Pp Tt Rr
c. YY Pp Tt Rr
d. Yy PP TT RR
Gamete variability depends on heterozygous gene pairs under Mendel’s law of independent assortment, where each heterozygous locus (Yy, Pp) doubles possible gamete combinations via the formula 2^n (n = heterozygous loci). Option b produces the highest variability with 16 gametes.
Gamete Calculation Method
Count heterozygous loci (different alleles like Yy) since homozygous (PP, TT) yield one allele type. Multiply 2 for each: monohybrid (Yy) = 2¹ = 2 gametes; dihybrid (YyRr) = 2² = 4; trihybrid = 8; tetrahybrid = 16. This creates genetic diversity in offspring.
Option Analysis
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a. Yy PP Tt Rr: Heterozygous at Y, T, R (n=3) → 2³ = 8 gametes (YPT, YPR, ypT, ypR, YPt, YPr, yPt, yPr).
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b. Yy Pp Tt Rr: Heterozygous at Y, P, T, R (n=4) → 2⁴ = 16 gametes (maximum diversity: all combinations like YPTR, YPT r, etc.).
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c. YY Pp Tt Rr: Heterozygous at P, T, R (n=3) → 2³ = 8 gametes.
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d. Yy PP TT RR: Heterozygous only at Y (n=1) → 2¹ = 2 gametes (Y, y).
Correct Answer
Option b. Yy Pp Tt Rr yields highest variability of gametes (16 types) due to four heterozygous loci assorting independently. This CSIR NET-style question tests understanding of genetic recombination basics.
