Diploid # is 46
Haploid # is 23
Females produce gametes with 22 autosomes plus an X
Males produce 2 types of gametes
1st 22 autosomes plus an X (produces daughters)
2nd 22 autosomes plus a Y (produces sons)
More than 50% of all spontaneous abortions are the result of chromosomal problems.
Common chromosomal problems
Down Syndrome: 2N = 47 45 autosomes + sex chromosomes (with trisomy for #21)
Kleinfelters Syndrome: 2N = 47 44 autosomes + XXY (male with Barr body)
Turners Syndrome: 2N = 45 44 autosomes + XO (female with no Barr body)
XYY Syndrome: 2N = 47 44 autosomes + XYY
How do males and females produce an equal dose from X chromosome?
Females have 2
Males have 1
Males use their X
Females use only one X
Inactivated X in females is visible in interphase as a distinct dark body. This is called the Barr body.
Mary Lyon’s hypothesis – Females inactivate one or the other X well into the development process.
Females are mosaics
Sex linked genes – genes that are on the sex chromosomes.
Hemophilia
Color blindness
Calico cats – always female
Male calico cats are very rare and are Kleinfelters Syndrome
In the case of female calico cats the mosaic pattern is seen on the hair color: orange and black. Since males get only one gene, they are either orange or black.
Olympics – females must prove they are female with 2 X’s. Some are XY females