Most scientific investigations use some form of the scientific method. Find out more about the scientific method. Science as defined above is sometimes called pure science to differentiate it from applied science, which is the application of research to human needs.
There are 13 chromosomes in a frog gamete and 26 in a frog body cell.
Mammals and Drosophila females have two X chromosomes: XX males have one X chromosome and one Y: XY These are the  sex chromosomes , all other chromosomes are called  autosomes . The sex with two different chromosomes is the heterogametic sex. The other is the homogametic sex. For the X chromosome then, female mammals and Drosophila have two copies of each gene on the X, but males have only one. Females can be homozygous or heterozygous, but males are hemizygous.