Y Chromosome - The Sex chromosome which is present only in the heterogametic sex, generally smaller than the X-chromosome and with a much smaller number of genes and having the opposite effect to the X-chromosome, all offspring produced by the uniting of Y -ganmetes with X-gametes being of the Y-sex.

Yeasts - Widely distributed unicellular fungi. They belong mainly to the Ascomycetes, which multiply typically by a budding process. The brewing and baking industries depend upon capacity of yeasts to secrets enzymes which convert sugars into alcohol and carbon dioxide. Yeasts are also used commercially as a source of proteins and vitamins.