Acho ndroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. Matthew has a family history of the condition, although he does not express the trait. Jane is an acho ndroplastic dwarf.

Matthew and Jane are planning a family of several children and want to know the chances of producing a child with acho ndroplastic dwarfism. If three children are born to Matthew and Jane, what are the chances that the first two children will not express the trait but that the third child will be an acho ndroplastic dwarf.

Question

Clay Villa

Social Studies

22 March, 16:48

Acho ndroplastic dwarfism is a dominant genetic trait that causes severe malformation of the skeleton. Homozygotes for this condition are spontaneously aborted (hence, the homozygous condition is lethal) but heterozygotes will develop to be dwarfed. Matthew has a family history of the condition, although he does not express the trait. Jane is an acho ndroplastic dwarf.

Matthew and Jane are planning a family of several children and want to know the chances of producing a child with acho ndroplastic dwarfism. If three children are born to Matthew and Jane, what are the chances that the first two children will not express the trait but that the third child will be an acho ndroplastic dwarf.

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Desmond Andrews · Answer 1

A punnet square can be described as a diagram which is used to illustrate the results of a cross. As the condition described, Mathew does not have Acho ndroplastic dwarfism hence he will have recessive alleles, aa. Jane has the condition so she will have the allele Aa (as the child with both AA is aborted). The punnet square for a cross between hem can be drawn as follows:

a a

A Aa Aa

a aa aa

There is 1/8 chance that the first two children will not express the trait but that the third child will be an acho ndroplastic dwarf.