Which of the following is/are correct for autosomal dominant inheritance? (i) Phenotype usually present in all generations (II) 50% risk to any child of an affected person (III) Unaffected relatives do not transmit the phenotype to their children (IV) No sex difference in transmission. Male to male transmission can occur Select one: a. I,II, III , IV b. I,II,III C. I d. 1,11

The correct answer is:<br /><br />c. I<br /><br />Explanation:<br />Autosomal dominant inheritance is characterized by the following features:<br /><br />(I) Phenotype usually present in all generations: This is correct. In autosomal dominant inheritance, the phenotype is typically present in every generation because only one copy of the dominant allele is required for the phenotype to be expressed.<br /><br />(II) 50% risk to any child of an affected person: This is incorrect. In autosomal dominant inheritance, the affected parent has a 50% chance of passing the dominant allele to each offspring, resulting in a 50% risk of the child being affected.<br /><br />(III) Unaffected relatives do not transmit the phenotype to their children: This is correct. Unaffected individuals do not have the dominant allele and therefore cannot transmit it to their children.<br /><br />(IV) No sex difference in transmission. Male to male transmission can occur: This is correct. Autosomal dominant traits are not linked to the sex chromosomes, so there is no difference in transmission between males and females. Male-to-male transmission is possible because the dominant allele is present on an autosome.<br /><br />Therefore, the correct answer is c. I.