Analysis: According to the meaning of the question, 1, 3,6 is male, 2,4,5 is female. First look at 3 and 4, the phenotype is normal, and the fifth one is sick, so the pathogenic gene is recessive. No.5 is sick and No.6 is normal, indicating that the pathogenic gene is located on the autosome. Assuming that the pathogenic gene A is dominant for A, then genotype 5 is Aa, and genotypes 3 and 4 are AA. Phenotype 6 is normal, and the genotype may be Aa. The probabilities are AA (1/3) and AA (2/3) respectively. When genotype 6 is Aa, if you marry a sick woman, you won't give birth to a sick boy. If genotype 6 is AA, the probability of marrying a sick girl and marrying a sick man is 1/2. Therefore, if the sixth of the third generation marries a sick woman, the probability of giving birth to a sick boy is1/3 * 0+2/3 *1/2 =1/3.