testcross
100 percent.
Given those conditions, the offspring have a 50% chance of demonstrating the dominant phenotype and a 50% chance of demonstrating the recessive phenotype.
The homozygous dominant individual can only pass on the dominant allele and the homozygous recessive individual can only pass on the recessive allele, therefore all offspring will be heterozygous and have the dominant phenotype.
Straight thumbs, hitch hiker's thumb is recessive...so the F1 generation in this example would be heterozygous and have the dominant (straight thumbed) phenotype.
Phenotype: Black Bear x Brown Bear Genotype: BB x bb Possible gametes: B B b b Possible B B crosses: b Bb Bb b Bb Bb Phenotype of offspring: Only Black bears
To determine the genotype of an individual showing the dominant phenotype, you would cross it with a homozygous recessive individual. This would help reveal whether the dominant phenotype individual is homozygous dominant or heterozygous for the trait.
Homozygous recessive.
100 percent.
To perform a testcross, you cross an individual with a dominant phenotype (but unknown genotype) with a homozygous recessive individual. By examining the offspring's phenotypes, you can determine the genotype of the unknown individual through the principles of Mendelian genetics. This allows you to determine if the individual is homozygous dominant or heterozygous for a specific trait.
Given those conditions, the offspring have a 50% chance of demonstrating the dominant phenotype and a 50% chance of demonstrating the recessive phenotype.
Codominance - when both alleles are expressed equally in an individual. This allows us to directly observe the genotypes of the individuals based on their appearance.
In a test cross, one individual with a dominant phenotype but unknown genotype is crossed with a homozygous recessive individual. The genotype of the individual with the dominant phenotype can then be inferred based on the phenotypic ratios of the offspring.
It is generally easier to analyze genotype by observing phenotype in organisms with complete dominance because the phenotypic expression directly reflects the genotype. In contrast, with incomplete dominance, the phenotype is an intermediate between the two homozygous genotypes, making it more challenging to accurately determine the genotype solely based on the phenotype.
The homozygous recessive individual is used in a test cross to determine the genotype of an individual with a dominant phenotype but unknown genotype. When crossed with a homozygous recessive individual, if any offspring display the recessive trait, it indicates that the unknown individual is heterozygous for that trait.
Phenotype
The genotype ratio is 1:2:1 (1 homozygous dominant, 2 heterozygous, 1 homozygous recessive) and the phenotype ratio is 3:1 (3 individuals showing the dominant trait, 1 individual showing the recessive trait).
The homozygous dominant individual can only pass on the dominant allele and the homozygous recessive individual can only pass on the recessive allele, therefore all offspring will be heterozygous and have the dominant phenotype.