A mutation that causes a yellowing of leaves in snapdragon
plants was discovered in the early 1900s. Plants with this
condition, termed aurea, have less chlorophyll than green
plants.
Crosses between various combinations of green and aurea plants
yielded the following results.
green x green = all green
aurea x aurea = 2/3 aurea, 1/3 green
green x aurea = 1/2 green, 1/2 aurea
With respect to snapdragon color,
what can be said of the G
and GAalleles?
The GA is dominant to the G allele
The G^A and G alleles exhibit codominance
The GA allele is recessive to the G allele
The GA and G alleles exhibit incomplete dominance
Answer
sry the ans is : The GA is dominant to the G
allele
Incomplete dominance occurs when the phenotype of the
heterozygous genotype is distinct from and often intermediate to
the phenotypes of the homozygous genotypes. For example, the
snapdragon flower color is either homozygous for red or white. When
the red homozygous flower is paired with the white homozygous
flower, the result yields a pink snapdragon flower. The pink
snapdragon is the result of incomplete dominance. A similar type of
incomplete dominance is found in the four o'clock plant wherein
pink color is produced when true-bred parents of white and red
flowers are crossed. In quantitative genetics, where phenotypes are
measured and treated numerically, if a heterozygote's phenotype is
exactly between that of the two homozygotes, the phenotype is said
to exhibit no dominance at all, i.e. dominance exists only
when the heterozygote's phenotype measure lies closer to one
homozygote than the other.
When plants of the F1 generation are self-pollinated,
the phenotypic and genotypic ratio of the F2 generation
will be 1:2:1 for both generations
GA is domainant to G allele