The temporal dynamics of processes underlying Y chromosome degeneration. How to cite and reference Link to this chapter Copy to clipboard. I will therefore refer to the W and Y as minor sex chromosomesand will use the term major sex chromosomes in reference to the X and Z. Ethics declarations Conflict of interest The authors declare that they have no conflict of interest.
Main article: Sex determination system. Namespaces Article Talk. It turns out that the sex determination pathway is probably more complicated and SRY may in fact inhibit some anti-male genes. Not all male-specific genes are located on the Y chromosome. In humans, half of spermatozoa carry X chromosome and the other half Y chromosome.
In the past, there wasn't much evidence supporting two kinds of sex chromosomes for a woman in Griffith idea that X-chromosome inactivation occurred due to dosage compensation.
The first clues to the existence of a factor that determines the development of testis in mammals came from experiments carried out by Alfred Jost who castrated embryonic rabbits in utero and noticed that they all developed as female.
Current Biology. Because females carry two identical chromosomes, they are considered the homogametic sex, while males, carrying two different types of sex chromosome, are called the heterogametic sex. The zygote is diploidmeaning that it contains two sets of chromosomes. Females are determined by two identical sex chromosomes: their genotype is XX.
In mammals, the presence of the Y determines maleness and the absence of a Y determines femaleness. New Phytol — Charlesworth D Plant sex chromosomes.