Several members of the family in the pedigree who suffered from a disease are colored in black.Currently deceased members of the family are struck out with a line.a. Based on the data in the pedigree, propose a Mendelian model that would explain the inheritance ofthis disease. Explain how the data is consistent with your model.b. A scientist hypothesizes that a mutation at a single locus is responsible for the pattern of inheritanceseen in this pedigree. Explain how a mutation in a gene can arise during meiosis. Describe onestrategy organisms use to prevent such mutations from arising.III Ø-IIITIIVof 22 Answered딤 F3F5@%23$4%2358WYSFG

A pedigree represents the genetic history of a family using different lines and symbols. It displays the biological relationships in a family and helps in the determination of inheritance pattern of genetic disorders. They are usually made by genetic counselors or geneticists to study the genetic history of a family.The given disease affects both male and female members of the family. However, the proportion of affected males is much higher than affected females. Since both males and females are affected by this disease, it cannot be Y-linked. The affected father in generation II produces three affected male children and one normal daughter from a marriage with a phenotypically normal female. From a second marriage, this affected male produces one affected son, one affected daughter, and one normal daughter. The genetic trait is not expressed in every generation therefore it must be a recessive trait that requires two mutant copies to express itself. The most probable model that can explain the inheritance of genetic disease shown in the pedigree is the X-linked recessive model of inheritance. The affected male in generation II must have a carrier heterozygous mother who exhibits a normal phenotype. The father of this male must be normal and male children receive only one X chromosome and too from their mother. Therefore, this affected male in generation II must have received a mutant disease-causing X allele from the mother and due to hemizygosity of males at this locus, the allele would be expressed to produce a disease phenotype. The female partners of this affected male would also be heterozygous carriers. Therefore, the affected male children in generation III would have received disease-causing X allele from their carrier mothers. One affected daughter would have received one diseasing causing X allele from the affected father and another one from the carrier mother.In meiosis, the homologous chromosomes undergo recombination/crossing-over during the prophase I stage. In some scenarios, unequal crossing over can happen to produce a duplicated chromosome copy and another deleted chromosome copy. Such unequal crossing-over events are initiated by chiasma formation between sites that do not share complete homology. Due to incomplete homology or partial homology, misalignment between homologous chromosomes can occur which produces one chromosomal copy with duplicated segment and another copy with the deleted segment. The recombination process involves the generation of double-stranded breaks (DSBs) across the genome. These breaks are aligned and positioned appropriately by the molecular machinery to generate cross-overs. One chromosomal copy is used as a template to synthesize DNA (deoxyribonucleic acid) on another copy. If misalignment occurs at these DSBs then gene mutations can arise. The cells use the recombinational repair strategy to resolve these mutations. In this process, the gap or mutations in one strand is repaired by using the wildtype homologous DNA as the template. This process of repair is called post-replication repair. The damaged site is repaired by taking a homologous intact strand from another duplex. After the exchange of single strands, one duplex carries the damaged/mutant strand and the newly repaired strand and another duplex carries both normal strands. The damaged strand is repaired by using the newly repaired strand as the template.