Quote (silvermace @ 3 Mar 2011 22:33)
a) Ss x Ss = SS;Ss;Ss;ss
Unknown male was homozygous not-spotted (ss). the cross would have been Ss x ss = 1:1 ratio of Ss and ss
2)
a)_cross black parent with white coat parent. See if the f1 generation is all black coat (Bb) or half black half white (1:1 Bb;bb)
black was heterozygous = Bb, white guinea pig = bb. 10 off spring = 1:1 ratio so 5:5 Bb and bb respectively
3)
a) EeHh x EeHh = 9:3:3:1 ratio (free earlobs + widows; free earloab + straight; attached earlobe + widow; attached + straight);
4)
man: GgAa; women: ggaa
25% chance of being both galactosemic and albino
Awesome
Understand all of them, saweet.
Couple more for you or anyone else.
7. A mutant sex-linked trait called notched (Xn) is deadly in female Drosophilia when homozygous. Males who have a single allele (Xn) will also die. The heterozygous condition (XNXn) causes small notches on the wing. The normal condition in both males and females is represented by the alleles Xn.
a) Indicate the phenotypes of the F1 generation from the following cross: XnXN x XnY
Explain why dead females are never found in the F1 generation, no matter which parents are crossed. Use a punnett square to help you.
c) Explain why the mating of a female XNXn and a male XNY is unlikely. Use a Punnett square to help you.
8. Cystic fibrosis is a life-threatening disease caused by a recessive allele (d). A normal child has the dominant allele (D). If a homozygous dominant male and a homozygous recessive female have children, what are the chances that their children will have cystic fibrosis? Is there a chance that their grandchildren could have a disease? Why or why not?
9. Polycystic kidney disease (PKD) is a genetic disorder caused by a dominant allele. This disease causes the kidney become packed with fluid filled growths, called cysts, which can severely impair kidney function. The pedigree below shows the inheritance of PKD in one family.
a) How many generations are shown in the pedigree chart?
b ) How many children were born to the parents in the first generation?
c) What are the genotypes of individual I-1 and I-2?
d) How is it possible that in generation II, some of the children showed symptoms of PKD while others did not?
e) Individuals II-6 and II-7 had a child without PKD. Does this mean they will never have a child with PKD? Explain your answer.