# monohybrid cross problem watch

1. the question is:

some cats fur color are sex linked.

when a ginger male cat crossed with blakc female, all female kittens were tortoiseshell( a pattern of black hair s and ginger), and all male kittens were black. however in the reciprocal cross, although all the female kittens were again tortoiseshell, the male kittens were ginger

XB= an X chromosome, carryin an allele for blakc hair
XG=an X chromosomme carryin an allele for ginger hair.

Cross 1

ginger male x black female

is this right for the parental genotype, XG XG X XBXB

what are the gametes? and how would u cross them?

Cross 2

Black Male x ginger female

again im unsure here for parental genotypes and the gametes

thanks
2. This is an AQA Exam Question I think. The answers (and full mark scheme) are therefore online. It is from module 4 (E,C&C) in January 2004.
3. (Original post by Akthar)
the question is:

some cats fur color are sex linked.

when a ginger male cat crossed with blakc female, all female kittens were tortoiseshell( a pattern of black hair s and ginger), and all male kittens were black. however in the reciprocal cross, although all the female kittens were again tortoiseshell, the male kittens were ginger

XB= an X chromosome, carryin an allele for blakc hair
XG=an X chromosomme carryin an allele for ginger hair.

Cross 1

ginger male x black female

is this right for the parental genotype, XG XG X XBXB

what are the gametes? and how would u cross them?
No those aren't the parental genotypes. Remember, males are XY so the genotype of the ginger male will be XGY and the balck female will be XBXB.

The gametes will therefore be:
XG
Y
XB
XB

Use a punnet square to cross them and you'll end with offsping with the following genotypes:

XBXG (tortoiseshell females) and XBY (black males)

--------------

(Original post by samd)
This is an AQA Exam Question I think. The answers (and full mark scheme) are therefore online. It is from module 4 (E,C&C) in January 2004.
So it is:

http://www.aqa.org.uk/qual/gceasa/qp...W-MS-Jan02.pdf

Go to page 4.

It's actually question 6 from the Jan 02 paper (Module 5).
4. That is strange!

It is also a question from January 2004 (Module 4) but on the AQA B specification. See the question (which is very similar to the one above) on page 10 of this document.

edit: Admittedly the questions are not identical, but they have the exact same context, and similar procedures are required.

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Updated: November 20, 2005
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