Neurofibromatosis 1 (NF1) is an autosomal dominant disorder inherited on human chromosome 17. Part of the analysis mapping the NF1 gene to chromosome 17 came from genetic linkage studies testing segregation of NF1 and DNA genetic markers on various chromosomes. A DNA marker with two alleles, designated 1 and 2, is linked to NF1. The pedigree below shows segregation of NF1 (darkened symbols) and gives genotypes for the DNA marker for each family member.

Based on the phase of alleles on chromosomes in generation II, is there any evidence of recombination among the eight offspring in generation III? Explain. <>

Key Concepts

Autosomal Dominant Inheritance

Autosomal dominant inheritance refers to a pattern where only one copy of a mutated gene from an affected parent can cause the disorder in offspring. In the case of Neurofibromatosis 1 (NF1), this means that an individual with the NF1 mutation has a 50% chance of passing it on to each child. Understanding this concept is crucial for analyzing pedigrees and predicting inheritance patterns.

Genetic Linkage and Markers

Genetic linkage occurs when genes are located close to each other on the same chromosome, leading to their alleles being inherited together more often than not. DNA markers, which are specific sequences of DNA with known locations, can help track the inheritance of linked genes. In the context of NF1, the presence of a DNA marker linked to the NF1 gene can provide insights into the inheritance patterns observed in the pedigree.

Recombination

Recombination is the process during meiosis where homologous chromosomes exchange genetic material, leading to new allele combinations. This can affect the inheritance of linked genes, such as the NF1 gene and its associated markers. By analyzing the genotypes of offspring in generation III, one can determine if recombination has occurred, which would indicate a separation of the linked alleles from the NF1 gene.