MadSci Network: Genetics

Re: genetic question of a zoot

Date: Wed Feb 7 11:27:58 2001
Posted By: Yvonne A. Simpson, Grad student, Pathology, Edinburgh University
Area of science: Genetics
ID: 980311493.Ge

Dear Cara, 
I am not too sure how the Americam education system works so I'm not too 
sure how old your brother is.  I think that his teachers are trying to get 
him to demonstrate a knowledge of genetic crosses, like Mendel's peas.

First, I am assuming that these'zoots' are imaginary - I've never heard of 
one.  We are dealing with three genes - one for colour, one for 
intelligence and one for height.  The different forms of the genes are 
called alleles so there are two alleles for each gene e.g. sort and shorter 
for the height gene.  

You have two test subjects.  Do you know what the terms homzygous and 
heterozygous mean?  If an organism is homozygouss the two alleles it has 
for the gene are the same.  e.g. two alleles for brown.  To be heterozygous 
is to have two different alleles -e.g. one for white and one for brown at 
the colour gene.  O.k. Assuming that the test subjects are homozygous, when 
they breed together, they can only pass on one of the alleles they have in 
their egg or sperm.  This means that zoot one can only pass on alleles for 
being brown, short and moronic and zoot two can only pass on alleles for 
being white, shorter and intelligent.  The offspring of this mating are 
therefore going to be heterozygous at each of the three genes - they will 
have  a mixture.  This is where the question about dominance comes in.  
Will the offspring be short or shorter, white or brown, intelligent or 
moronic.  Whatever the offspring look like will answer whether brown or 
white is dominant - if it is brown then the brwon allele is dominant and 
vice versa.  If it is intelligent then the allele for intelligence is 
dominant or vice versa if it is moronic and if it is short then the allele 
for being short is dominant or vice versa if it is shorter.  

Now, I'll give a little extra here and you judge for yourself if this is 
for your brother's age or not.  I think the reason why they mention some 
zoots are shiny and tan is because they may be wanting your brother to 
realise that these are mutants with different versions of the height and 
colour alleles.  A height allele for tall and a colour allele for tan.  

I hope this has answered your question.  Check out chi-squares, genetic 
crossing  and mendel's peas for more info - do a web search if there is 
nothing in your school text  book.    

Best wishes, 

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