The pedigree below shows the occurrence in a family of a rare, autosomal recessi

Question

The pedigree below shows the occurrence in a family of a rare, autosomal recessive disease.

a)Use appropriate symbols on the pedigree above to show which individuals are known to be

carriers of the disease-causing allele. [2 marks]

b)What is the probability that individual IV.1 will have the disease? Explain. [4 marks]

c)Explain why matings like that between III.4 and III.5 (i.e. consanguineous matings) are not generally advised. [2 marks]

a)Use appropriate symbols on the pedigree above to show which individuals are known to be

carriers of the disease-causing allele. [2 marks]

b)What is the probability that individual IV.1 will have the disease? Explain. [4 marks]

c)Explain why matings like that between III.4 and III.5 (i.e. consanguineous matings) are not generally advised. [2 marks]

Explanation / Answer

In the first generation male is affected.

In the second generation the second,third and fifth all girls are carriers.

In the third generation the second child is affected,fourth and fifth child are carrier.

In the fourth generation child may be affected but it's gender is not specified.

b) In the third generation the fourth girl is the carrier but the fifth boy being a normal or affected individual will be 1/2 so it depends on the fifth male being affected by the disease.

c)Consanguineous marriages are generally not advised because it increases the chance of recessive and multifactorial disorders have the highest value.

Still births,child deaths and recurrent abortions are much greater in this case.

The more closer the biological relationship between parents more chances of acquiring similar character and defective recessive Gene.

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