One form of male sterility in corn is maternally transmitted. Plants of a male-sterile line crossed with normalpollen give male-sterile plants. In addition, some lines ofcorn are known to carry a dominant nuclear restorer allele (Rf ) that restores pollen fertility in male-sterile lines.a. Research shows that the introduction of restoreralleles into male-sterile lines does not alter or affectthe maintenance of the cytoplasmic factors for malesterility. What kind of research results would lead tosuch a conclusion?b. A male-sterile plant is crossed with pollen from aplant homozygous for Rf. What is the genotype of theF1? The phenotype?c. The F1 plants from part b are used as females in atestcross with pollen from a normal plant (rf/rf ). Whatare the results of this testcross? Give genotypes andphenotypes, and designate the kind of cytoplasm.d. The restorer allele already described can be calledRf-1. Another dominant restorer, Rf-2, has been found.Rf-1 and Rf-2 are located on different chromosomes.Either or both of the restorer alleles will give pollenfertility. With the use of a male-sterile plant as a tester,what will be the result of a cross in which the maleparent is(1) heterozygous at both restorer loci?(2) homozygous dominant at one restorer locus andhomozygous recessive at the other?(3) heterozygous at one restorer locus and homozygousrecessive at the other?(4) heterozygous at one restorer locus and homozygousdominant at the other?
One form of male sterility 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 ) that restores pollen fertility in male-sterile lines.
a. Research shows that the introduction of restorer
alleles into male-sterile lines does not alter or affect
the maintenance of the cytoplasmic factors for male
sterility. What kind of research results would lead to
such a conclusion?
b. A male-sterile plant is crossed with pollen from a
plant homozygous for Rf. What is the genotype of the
F1? The phenotype?
c. The F1 plants from part b are used as females in a
testcross with pollen from a normal plant (rf/rf ). What
are the results of this testcross? Give genotypes and
d. The restorer allele 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.
Either or both of the restorer alleles will give pollen
fertility. With the use of a male-sterile plant as a tester,
what will be the result of a cross in which the male
parent is
(1) heterozygous at both restorer loci?
(2) homozygous dominant at one restorer locus and
homozygous recessive at the other?
(3) heterozygous at one restorer locus and homozygous
recessive at the other?
(4) heterozygous at one restorer locus and homozygous
dominant at the other?
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