He has a homozygous genotype
Dominant. he has a homozygous genotype
It was said earlier that, "Unattached earlobes are the dominant trait, twice as many people have unattached earlobes compared to attached." There is not actually any real proof that unattached earlobes are dominant. While more people may have unattached earlobes, attached earlobes are dominant. This was proved in a pedigree which covered three generations of extended families.
Examples of dominant genes include brown eyes and attached earlobes, where the dominant allele will be expressed over its recessive counterpart. Recessive genes include blue eyes and detached earlobes, which will only be expressed when an individual has two copies of the recessive allele.
If a boy is born with attached earlobes, he must have inherited two recessive alleles (ee), one from each parent. This means that both parents must either be carriers of the recessive allele (Ee) or express the attached earlobe phenotype themselves (ee). Therefore, at least one of the parents must have the recessive allele for attached earlobes.
Person A must carry at least one dominant allele for unattached earlobes, as they are not shaded gray and therefore do not express the recessive trait of attached earlobes. If A had two recessive alleles, they would exhibit the attached earlobe trait. Additionally, A could be homozygous dominant or heterozygous for the trait, meaning they might have a parent or sibling with attached earlobes as a result of inheriting the recessive allele.
If your friend has attached earlobes (recessive trait), then your friend must have two copies of the recessive allele for attached earlobes (aa). This means that both of your friend's parents must be carriers of the recessive allele (Aa) in order to pass it on. Your friend's mother and father would both have one dominant allele (A) for free-hanging earlobes and one recessive allele (a) for attached earlobes.
The phenotypes of attached and unattached earlobes do not fit neatly into the Mendelian theory of two alleles for one trait, and there is a continuum of earlobe phenotypes. That said, unattached earlobes are a dominant trait, so if the individual is homozygous for unattached earlobes, all of her offspring will have the unattached phenotype, even if some or all of them are heterozygous.
Genotypes (phenotype) 25% homozygous dominant (free earlobes) 25% homozygous recessive (attached earlobes) 50% heterozygous (free earlobes) 75% phenotypically dominant (free earlobes) 25% phenotyically recessive (attached earlobes) Ratios Genotype 1:1:2 Phenotype 3:1
If both you and your sibling have attached earlobes (aa genotype) and your parents have unattached earlobes, then your parents must both be carriers of the recessive allele for attached earlobes (Aa genotype).
If two parents with free earlobes have a child with attached earlobes, both parents must have the genotype of heterozygous (Ee) for earlobe shape. Free earlobes (E) is dominant over attached earlobes (e), so the presence of attached earlobes in their child indicates that both parents are carriers of the recessive allele for attached earlobes.
a male with one recessive allele
Approximately 30% of the population has attached earlobes. This trait is determined by genetics, with some studies suggesting that it follows a simple dominant-recessive pattern.