Question

One form of male sterility (Ms) in corn is maternally transmitted. Plants of a male sterile line crossed with normal pollen give male-sterile plants. In addition, some lines of corn are known to carry a dominant nuclear restorer allele (Rf-1) that restores pollen fertility in male sterile lines. Another dominant restorer (Rf-2) has been found on a different chromosome. Either or both of the restorer alleles will restore pollen fertility in male sterile lines.

A male-sterile plant is crossed with pollen from a plant homozygous for Rf-1. An F1 plant from this cross is used as the ovule donor, and crossed with pollen from a normal plant (rf-1/ rf-1). What phenotypes are produced by this cross?

the ANSWER is fetile females; 1/2 fertile males; 1/2 sterile males

I was just wondering if you could explain this answer? Thanks!

Answer 1

Typical cytoplasm is shown [n] and male-sterile cytoplasm is [ms]. The way to this issue is to understand that there is an atomic quality (Rf) isolating in Mendelian form and an organelle isolating in non-Mendelian (maternal) design. Eggs from male-sterile plants result in more male-sterile plants, paying little respect to the genotype of the dust with which they are treated. This male-sterile imperfection can be overcome if the core contains no less than one duplicate of the predominant Rf restorer allele. To do the issue, set up the cross as: rf/rf [ms] female X Rf/Rf [doesn't matter] male. The plant from which the egg comes must be rf/rf or it would not be "male-sterile", as the issue demonstrates. The cytoplasm of the dust doesn't make a difference as a result of the maternal legacy. Presently, decide the atomic and cytoplasmic genotypes of the F1 coming about because of the cross. Utilize Mendelian hereditary qualities to decide the genotype of the restorer locus. Utilize uniparental, maternal legacy to decide the genotype of the cytoplasm. When you have the genotypes, decide the phenotype of the plant in view of the cytoplasm genotype and regardless of whether it is "reestablished".

Rf/+; MSt females x +/+ males would generate 1/2 male sterile +/+;
MSt males and 1/2 male fertile Rf/+; MSt
The restorer gene already described can be called Rf-1. Another
dominant restorer, Rf-2, has been found. Rf-1 and Rf-2 are located on
different chromosomes.