Current location - Quotes Website - Famous sayings - When Mendel said different pairs of genetic factors, he meant whether the alleles were right or wrong.
When Mendel said different pairs of genetic factors, he meant whether the alleles were right or wrong.
A, Mendel's paired genetic factors refer to alleles, and different pairs of genetic factors refer to non-alleles on non-homologous chromosomes, and A is wrong;

B, Mendel thinks that YyRr plants can produce four kinds of female gametes and four kinds of male gametes, which are yr, yR, Yr, YR respectively, and the ratio is1:1.B is correct;

C, the variation of alleles on homologous chromosomes cross-exchanged by non-sister chromatids in tetrad stage belongs to gene recombination, and C is wrong;

D the chromosome number of human cells is 2N in the process of subtracting Ⅰ, n in the early, middle and late stages of subtracting Ⅱ, and 2N in the late stage of subtracting Ⅱ. D is wrong.

Therefore, choose: B.