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Name: Fauzia Khan
Status: Educator
Age: 30s
Location: N/A
Country: N/A
Date: April 2003


Question:
What is the difference between autosomes and sex chromosome and thier functions?



Replies:
Autosomes are any chromosomes other than the sex chromosomes. They serve no special function except that they each contain different genetic instruction. The sex chromosomes are distinguished from the others because one gene on the Y( that activates another set of genes) is the SRY, or sex-determining region of the Y, gene. When this gene turns on it begins the male pattern of development. So far, the going information is that if there is no SRY to turn on, the "default" pattern the embryo becomes female. Some scientists are skeptical of this, however, and are searching for a "sex-determining" gene in females, perhaps on the X. Even though the X doesn't contain a sex determining gene (that we know of!), it pairs with the Y during meiosis and they do exchange a small amount of information during crossing over. The combination of the two chromosomes determines sex of the offspring in humans.

vanhoeck


Interesting question and far more complex than it might seem. Aside from the sex chromosomes producing certain proteins that obviously affect sexual development (i.e., the sry gene on the Y chromosome) the "sex chromosomes"...especially the X chromosome have genes for all sorts of functions as do the autosomes. The Y chromosome (about 59 million bases) is a little different because it is so small ( chromosome #1 has 263 million bases!). The Y has very few genes...the sry and some genes for sperm production and what some seem to think is a lot of junk. The X chromosome is much larger than the Y at 164 million bases. There are entire books written on this subject and anywhere near a comprehensive understanding of the interaction of proteins produced by the genes of different chromosomes is many decades away...and might not even be possible...something like what I call incomprehensible complexity. The X, by the way, has a gene involved with prostate cancer.

Peter f


The autosomes are the general chromosomes that carry the information to make a human being. They all come in pairs (one set from mom, one set from dad).

The sex chromosomes also come in pairs, but come in two types -- X and Y. In humans, the Y chromosome carries the information for a few hormones and receptors that make an XY embryo develop male characteristics. An XX embryo lacks the "testis determining factor" and develops as female.

The process is further complicated because the female carries 2 X chromosomes while the male has only 1. So in mammals, one of the two X chromosomes in females gets inactivated. This is why calico cats are virtually always female - one X chromosome carries the gold color and the other X chromosome carries the black color. If the gold chromosome is shut off, the fur is black. If the black is shut off, the fur is gold. A male could carry either the black or the gold chromosome, but not both since he's XY. So in males, no chromosome gets shut off.

Christine Ticknor, Ph.D.
Ireland Cancer Center
Case Western Reserve University



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