A diseased man marries a normal woman. They get three daughters and five sons. All the daughters were diseased and the sons were normal. The gene of this disease is:

1. Sex-linked dominant

2. Sex-linked recessive

3. Sex-limited character

4. Autosomal dominant

Which of the following discoveries resulted in a Nobel Prize:

1. X-rays induce sex-linked recessive lethal mutations

2. Cytoplasmic inheritance

3. Recombination of linked genes

4. Genetic engineering

The recessive genes located on X-chromosomes in humans are always:

1. Sub-lethal

2. Expressed in males

3. Expressed in females

4. Lethal