You asked: What allele contributes to the phenotype only when two copies of it are present?

What are the two alleles that control the phenotype of a trait?

Genetics Vocabulary

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genotype the genetic makeup
homozygous an organsm with two alleles for a trait that are exactaly the same
heterozygous an organism that has two different alleles for a trait
phenotype the physical trait that shows as a result of a particular genotype

When both alleles are seen in the phenotype it is called?

Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. … In codominance, however, neither allele is recessive and the phenotypes of both alleles are expressed.

Why does an individual always have only two alleles for a given gene?

Since diploid organisms have two copies of each chromosome, they have two of each gene. Since genes come in more than one version, an organism can have two of the same alleles of a gene, or two different alleles. This is important because alleles can be dominant, recessive, or codominant to each other.

How do we obtain two copies of each gene?

You get one copy of each of your chromosomes from your mother and one from your father. This is how you get two copies of most every gene. has unique chromosomes. Chromosomes are passed onto children in a complicated process called meiosis.

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When the 2 alleles of a trait are different?

An organism which has two different alleles of the gene is called heterozygous. Phenotypes (the expressed characteristics) associated with a certain allele can sometimes be dominant or recessive, but often they are neither.

When two alleles are different they are?

An allele is one of two or more versions of a gene. An individual inherits two alleles for each gene, one from each parent. If the two alleles are the same, the individual is homozygous for that gene. If the alleles are different, the individual is heterozygous.

What determines or contributes to your phenotype?

An organism’s phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes. … Phenotypes also include observable characteristics that can be measured in the laboratory, such as levels of hormones or blood cells.

Are both alleles expressed?

In most cases, both alleles are transcribed; this is known as bi-allelic expression (left). However, a minority of genes show monoallelic expression (right). In these cases, only one allele of a gene is expressed (right).