How sex chromosomes decide sex despite having the same DNA as autosomes?
All diploid organisms with allosome-determined sex get half of their allosomes from each of their parents. In mammals, females are XX, they can pass along either of their X’s, and since the males are XY they can pass along either an X or a Y. For a mammal to be chromosomally female, the individual must receive an X chromosome from both parents, whereas to be chromosomally male, the individual must receive a X chromosome from their mother and a Y chromosome from their father. It is thus the male’s sperm that determines the sex of each offspring in humans.
An autosome is a chromosome that is not an allosome (a sex chromosome). The members of an autosome pair in a diploid cell have the same morphology unlike those in allosome pairs which may have different structure.
For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosomepair pair (46 chromosomes total). The autosome pairs are labeled with numbers (1–22 in humans) roughly in order of their sizes in base pairs, while allosomes are labelled with their letters. By contrast, the allosome pair consists of two X chromosomes in females or one X and one Y chromosome in males. (Unusual combinations of XYY, XXY, XXX, XXXX, XXYY or XXXXX, among other allosome combination , are known to occur and usually cause developmental abnormalities.)
Autosomes still contain sexual determination genes even though they are not sex chromosomes. For example, the SRY gene on the Y chromosome encodes the transcription factor TDF and is vital for male sex determination during development. TDF functions by activating the SOX9 gene on chromosome-17, so mutations of the SOX9 gene can cause humans with a Y chromosome to develop as females.
An autosome is a chromosome that is not an allosome (a sex chromosome). The members of an autosome pair in a diploid cell have the same morphology unlike those in allosome pairs which may have different structure.
For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosomepair pair (46 chromosomes total). The autosome pairs are labeled with numbers (1–22 in humans) roughly in order of their sizes in base pairs, while allosomes are labelled with their letters. By contrast, the allosome pair consists of two X chromosomes in females or one X and one Y chromosome in males. (Unusual combinations of XYY, XXY, XXX, XXXX, XXYY or XXXXX, among other allosome combination , are known to occur and usually cause developmental abnormalities.)
Autosomes still contain sexual determination genes even though they are not sex chromosomes. For example, the SRY gene on the Y chromosome encodes the transcription factor TDF and is vital for male sex determination during development. TDF functions by activating the SOX9 gene on chromosome-17, so mutations of the SOX9 gene can cause humans with a Y chromosome to develop as females.
