Royal Family Pedigree Chart for Haemophilia?
I’m taking Biology 30 and having a few issues understanding the pedigree charts!
We’re supposed to figure out the genotypes and phenotypes of as many ‘royals’ as we can in this chart we were given. If there are multiple possibilities we need to list them. If you can help me out with it would be great!
thank you so much!
Haemophilia is carried on the X chromosome – call XH a chromosome with a normal gene and Xh a chromosome with the haemophilia gene.
Males have only 1 X chromosome which they inherit from their mother (they get a Y from their father) – if they have the haemophilia allele they have the disease, if they don’t they are normal. In a pedigree, affected individuals are shaded, males are squares, females circles.
Normal males are XHY, affected males are XhY.
Mothers who are normal themselves (carriers) but have an affected son are XHXh, they pass on the normal chromosome to normal sons and affected chromosome to affected sons.
So the only people we can’t be sure about are daughters of female carriers, with normal fathers. All inherit a normal chromosome from their father XH, but could inherit XH or Xh from their mother, so could be either XHXH or XHXh.