|MadSci Network: Zoology|
The way you are telling roosters from hens (watching behavior) is probably the simplest and easiest way. The way to tell a rooster chick from a hen chick without making any mistakes is to somehow look at their genes. In birds, gender is determined by the types of chromosomes that they have. The chromosomes are the long strings of DNA that are found in the nucleus of every living cell. In all animals the chromosomes exists as pairs, with one copy coming from the mother and one from the father. One pair of chromosomes will determine the gender of the chicken. If these chromosomes are the same (called ZZ) the bird will be male. If these chromosomes are different (called ZW) then the bird will be female. No one knows exactly how this works, but the genes that are on these chromosomes control the gender of the bird. Unfortunately, to examine the genes in the birds to determine their gender would require a very expensive and complicated molecular biology lab.
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