Need help analyzing a pedigree

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lolPirate
Garter
Posts: 4
Joined: Mon Nov 23, 2009 9:50 pm

Need help analyzing a pedigree

Ok so I have this homework problem where I need to analyze the following pedigree and then identify the genotypes for certain individuals. I am not really sure how to tell if something is homozygous or heterozygous so I was hoping I could get some help. Here is the problem and the pedigree....

The pedigree below traces the inheritance of alkaptonuria, a biochemical disorder. Affected individuals,
indicated here by the colored circles and squares, are unable to metabolize a substance called alkapton, which
colors the urine and stains body tissues.

*Edit* I just realized that it gets cut off on the right side and that is where Michael is. He is an non affected male

(a) Is alkaptonuria caused by a dominant allele or by a recessive allele?

I think it is recessive right?

(b) Based on your analysis of the pedigree, what is the genotype of the following individuals? Use the term
homozygous domonant, heterozygous or homozygous recessive to describe the individual's genotype. In
addition, explain briefly how you know that that is their genotype.

(i) Michael- For this one I put heterozygous because neither of the parents express the trait but the daughter does

(ii) Sam-

(iii) Christopher-
(

c) Suppose Tina's father is unable to metabolize alkapton, what is the probability that Christopher is a
carrier of the allele causing alkaptonuria? Show me how you arrived at this answer by using a punnett
square. Label the columns and rows accordingly

For this one I have..
__A__|_a
A|AA |Aa
a|Aa |aa

I read the thing about asking for homework help first and I am pretty sure this was ok to post if not then sorry.

JackBean
Inland Taipan
Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm
what about to post only the link to the picture?
http://www.e-imagesite.com/Files2/fuckbio7445303.bmp
Or set the picture as smaller?
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

JackBean
Inland Taipan
Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm
a) http://www.lmgtfy.com/?q=alkaptonuria
yes, it is
b)
i) yes
ii) her mother is homozygous recessive, her father is heterozygous (thus children can, but don't have to be affected), if she's not affected, what genotype she has?
iii) Tom is homozygous recessive, and both his children are unaffected, so his wife must be homozygous dominant, so both childrens are heterozygous (the mother could be heterozygous as well, but both children must get good allele from her anyway). If Alan is heterozygous, his kid can be either heterozygous or homozygous dominant, you can't say for sure
c) yes, so what is the probability?
(quite stupid first ask about his genotype and then ask with what probability... )
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

lolPirate
Garter
Posts: 4
Joined: Mon Nov 23, 2009 9:50 pm

Re: Need help analyzing a pedigree

Awesome thanks for the help Jack. So if my square is correct for part three then the answer would just be 1/4 right?

JackBean
Inland Taipan
Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm
The question is about being carrier, not a homozygot. Thus, you must account each case, when having at least 1 a allele. I'm not sure, whether homozygot (aa) is taken as carrier as well, so the answer is either 50% (if not) or 75% (if yes).
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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