Question

why did morgan refer to males as hemizygous? x chromosome carries no gene y chromosome carries no gene females carry all genes males carry all genes

Explanation:

To determine why Morgan referred to males as hemizygous, we analyze each option:

• Option "X chromosome carries no gene": Incorrect. The X chromosome carries many genes.
• Option "Y chromosome carries no gene": Males have one X and one Y chromosome. The Y chromosome has relatively few genes, and for most X - linked genes, males have only one copy (since they have one X and the Y doesn't carry the corresponding alleles for most X - linked genes). This means males are hemizygous for X - linked genes as they have only one set of alleles for those genes (unlike females who have two X chromosomes and thus two sets of alleles for X - linked genes).
• Option "females carry all genes": Incorrect. No individual carries all genes, and this is not related to the concept of hemizygosity in males.
• Option "males carry all genes": Incorrect. Males do not carry all genes, and this is not related to hemizygosity.

Answer:

B. Y chromosome carries no gene (Note: More accurately, the Y chromosome carries very few genes related to X - linked traits, so for most X - linked genes, males have only one allele (from the X chromosome) as the Y doesn't have a corresponding allele, making them hemizygous. Among the given options, this is the most appropriate as the other options are clearly incorrect.)