Part III

1. There are three different genotypes possible when the male parent carries a dominant marker allele on the chromosome that participated in the A-B reciprocal translocation and the male fertilization a homozygous recessive female for the locus of interest.
   
   
2. A maternal effect is apparent when different phenotypes are expressed as the result of reciprocal crosses. The maternal effect can be caused by maternal tissue. The genotype of the maternal parent is expressed in maternal tissue. Pericarp tissue and hilum tissue is maternal tissue. Endosperm and aleurone is not maternal tissue. When reciprocal crosses are developed and the parents have different genotypes, reciprocal differences are due to the different genotypes of the maternal parent. Maternal effects only exist for one generation because the progeny generation (F₂) has a different maternal parent than the maternal parent of the F₁ seed.
   
   
3. Maternal inhertiance is apparent when different phenotypes are expressed as the result of reciprocal crosses. DNA located in cytoplasmic organelles is the cause of maternal inheritance. The pollen parent contributes very little cytoplasm to the zygote. As a result, the chloroplast and mitochondria genotype is almost entirely determined by the female parent. Maternal inheritance continues generation after generation. When the progeny from reciprocal crosses are different and the trait is inherited maternally, this is because the cytoplasmic organelle DNA genotypes are different between the parents.
   
   
4. Xenia is the immediate expression of the genotype of the pollen on endosperm tissue. Xenia is not due to maternal effect or maternal inheritance.
   
   
5. The bridge-breakage-fusion cycle results in variegated sectors, depending on where the break occurred during mitosis. The bridge-breakage-fusion cycle results from fusion of the ends of sister chromatids to produce dicentric chromosomes.
   
   
6. The Ds allele can cause a chromosome segment to break at the location of the Ds allele. The Ds allele will not cause a break or dissociation of a chromosome segment unless the autonomous Ac element is also present in the nucleus. The Ac element is autonomous because it does not require another element to function. Whe the Ac-Ds system causes a chromosome dissociation, a bridge-breakage-fusion cycle can begin in endosperm tissue.