Specialized chromosomes determine sex.
Study of meiosis revealed the chromosomal basis of sex.
People had long philosophized about the observed differences between males and females of a species. If one considers sex a trait, or set of traits, then it followed that sex is inherited. In 1905, closer study of meiosis revealed the chromosomal basis of sex. Scientists noticed an oddball pair among the homologous chromosomes lined up at the cell equator during reduction division. One chromosome (X) was much bigger than the other (Y). In human beings, this mismatched pair of one X and one Y chromosome is seen exclusively in male cells. A matched pair of X chromosomes is found in female cells. Thus, XX chromosomes determine femaleness, and XY chromosomes determine maleness. Females produce only eggs with X chromosomes; males produce sperm with an X or a Y chromosome.
xx chromosomes, xy chromosomes, x chromosomes, cell equator, female cells, male cells, chromosomal basis of sex, homologous chromosomes
- ID: 16249
- Source: DNALC.DNAFTB
DNAFTB Animation 9: Nettie Stevens and Edmund Wilson explain how biological sex is determined by special chromosomes.
Offspring arise from the union of specialized sex cells â a female egg and a male sperm.
DNA is organized into 46 chromosomes including sex chromosomes, 3D animation
DNAFTB Animation 8: Theodor Boveri presents chromosomes' role in development.
DNAFTB Problem 8: Take a look at human chromosomes.
"Fig. 6. The chromosomes of man"
DNAFTB Problem 9: Try your hand at sex determination.
The two genes that produce red and green light-sensitive proteins are located on the X chromosome.
(2 of 4) Cell dividing: chromosomes are visible and lined up at the plane of division.
(3 of 4) Cell dividing: chromosomes are being pulled toward the cellular poles.