Ijmb Model Questions Vol1 2023 Biology Question 10

Practice essay / theory question 10 from the 2023 Ijmb Model Questions Vol1 Biology examination. This question covers Mendelian inheritance, Pedigree analysis, Linkage and recombination, Molecular genetics of recessive disorders, Genetic counselling .

Ijmb Model Questions Vol1 2023 Biology Essay / Theory
Topics: Mendelian inheritance Pedigree analysis Linkage and recombination Molecular genetics of recessive disorders Genetic counselling
Question 10 IJMB_MODEL_QUESTIONS_VOL1 • 2023 • BIOLOGY • essay

A pedigree analysis is carried out for a rare autosomal recessive disorder, hereditary neuropathy, in a large extended family. The disorder manifests only when an individual is homozygous recessive (nn). In the pedigree, affected individuals are observed in two successive generations, and a consanguineous marriage is recorded.

Question Parts

( a )
Calculate the probability that a child of the marriage between two heterozygous carriers will be affected.
( b )
The disease gene is located on chromosome 12 and shows complete linkage with a marker locus M (alleles M1 and M2) with a recombination frequency of 5 %. A test cross is performed between an individual heterozygous for both the disease allele and the marker (nM1 / NM2) and a homozygous recessive individual (nnM2M2). Predict the phenotypic ratio of the offspring.
( ) List the possible gametes produced by the heterozygous parent, taking recombination into account.
( ) From the gamete list, derive the expected phenotypic ratio among the progeny.
( c )
Discuss two molecular mechanisms that could lead to the observed autosomal recessive inheritance pattern, and explain how each mechanism would be detected in a laboratory setting.
( d )
Propose a genetic counselling strategy for the family, highlighting the role of carrier testing and prenatal diagnosis.

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About This Question

This is Ijmb Model Questions Vol1 2023 Biology Question 10. It is one of the essay questions from the 2023 Ijmb Model Questions Vol1 Biology examination.

The question covers Mendelian inheritance, Pedigree analysis, Linkage and recombination, Molecular genetics of recessive disorders, Genetic counselling .

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