a. The Marfan’s syndrome is a dominant autosomal trait inherited. It is supported by the fact that almost half of the children of all affected individuals express the trait. If it is recessive then the individuals marrying affected spouses would become heterozygous for an allele. When the same allele is found in homozygous condition, the condition of Marfan’s syndrome would be expressed.
b. The pedigree replicates both Pleiotropy and variable expressivity. Penetrance may be represented as the percentage of individuals having specific genotypes expresses their associated phenotype. The pedigree has no evidence of any decreased penetrance.
c. Pleiotropy indicates that the gene product is necessary for the necessary functioning of a number of different tissues, organs, or processes. When there is a defect in the gene as a result of mutation the tissues, organs etc would be devoid of the gene product and would be affected ultimately.
Variable expressivity of a given phenotype from a specified genotype indicates modification by one or more genes, random noise, or environmental effects.