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In a dominant-recessive inheritance, an average of 25% are homozygous with the dominant trait, 50% are heterozygous showing the dominant trait in the phenotype (genetic carriers), 25% are homozygous with the recessive trait and therefore express the recessive trait in the phenotype. The genotypic ratio is 1: 2 : 1, and the phenotypic ratio is 3: 1.
Since the homozygous recessive individual can only pass on recessive alleles, the allele the individual in question passes on determines the phenotype of the offspring. [3] Thus, this test yields 2 possible situations: If any of the offspring produced express the recessive trait, the individual in question is heterozygous for the dominant ...
Figure 1: Inheritance pattern of dominant (red) and recessive (white) phenotypes when each parent (1) is homozygous for either the dominant or recessive trait. All members of the F 1 generation are heterozygous and share the same dominant phenotype (2), while the F 2 generation exhibits a 6:2 ratio of dominant to recessive phenotypes (3).
The individual has both a genetic predisposition for the dominant trait and a genetic predisposition for the recessive trait, and the dominant expression prevails in the phenotype. In an individual which is heterozygous regarding a certain allele, it is not externally recognisable that it also has the recessive allele.
The phenotype of a homozygous dominant pair is 'A', or dominant, while the opposite is true for homozygous recessive. Heterozygous pairs always have a dominant phenotype. [11] To a lesser degree, hemizygosity [12] and nullizygosity [13] can also be seen in gene pairs.
An individual that is homozygous-recessive for a particular trait carries two copies of the allele that codes for the recessive trait. This allele, often called the "recessive allele", is usually represented by the lowercase form of the letter used for the corresponding dominant trait (such as, with reference to the example above, "p" for the ...
If both alleles are the same, the genotype is referred to as homozygous. If the alleles are different, the genotype is referred to as heterozygous. Genotype contributes to phenotype, the observable traits and characteristics in an individual or organism. [3] The degree to which genotype affects phenotype depends on the trait.
The phenotype is a general term that defines an individual's visible, physical traits. The genotype of an offspring is known as its genetic makeup. The alleles of genes can either be dominant or recessive. A dominant allele needs only one copy to be expressed while a recessive allele needs two copies (homozygous) in a diploid organism to be ...