Question

Create A Pedigree

Ray and Elaine were married in 1970. They both had normal
vision. They had 2 daughters and then a son. Both
daughters, Alicia and Candace, had normal vision and never
had any children of their own. The son, Mike, was
colorblind. The son married Beth who also had normal
vision and they had 2 children of their own, first Greg then
Victoria. Victoria was colorblind, but Greg was not.
. Colorblindness is an X-linked recessive trait.
▪ Females need to inherit both defective X alleles to be color
blind. If females have one defective X allele, she is a carrier,
and if males have the defective X allele, he is color blind.
label genotypes and names.

Answer 1

To create a pedigree for color blindness, we must consider the inheritance pattern of the X-linked recessive trait. Ray and Elaine have two carrier daughters and a colorblind son, which indicates that Elaine is a carrier. Mike and Beth, both carriers, have a colorblind daughter and a non-colorblind son, further supporting this genetic pattern.

Step-by-step explanation:

To create a pedigree for color blindness, one must understand that color blindness is an X-linked recessive trait. In this scenario, Ray and Elaine both have normal vision and therefore do not show the phenotype for color blindness. They have three children: two unaffected daughters and an affected son, Mike. Since Ray has normal vision, it can be concluded that neither Ray nor Elaine has the affected gene, but Elaine could potentially be a carrier.

Alicia and Candace, the daughters, both have normal vision and are likely carriers, as they could have inherited the recessive allele from Elaine, assuming she is a carrier. Mike, the son, is colorblind, which confirms that his mother must be a carrier of the trait. Mike's wife, Beth, has normal vision, so their children have the following possibilities: if Beth is not a carrier, their son Greg will not be colorblind, and their daughter Victoria can only be a carrier but will not be colorblind. However, Victoria is colorblind, which leads to the conclusion that Beth must also be a carrier.

Therefore, the pedigree would show Ray (XY/XN) married to Elaine (XN/Xc), with daughters Alicia (XN/Xc) and Candace (XN/Xc), and a son Mike (XcY). Mike is married to Beth (XN/Xc) with two children: Greg (XNY) and Victoria, who is colorblind (XcXc).