How can the alleles that control that trait be described

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Alleles are copies of genes that influence hereditary characteristics. Each person inherits at least two alleles for a particular gene—one allele from each parent. They are also called allelomorphs. A good example of how alleles are expressed is eye color; whether we have blue or brown eyes depends on the alleles that are passed down from our parents.

Alleles play a big role in determining our inherited traits, along with DNA and genes. Deoxyribonucleic acid DNA is the hereditary material that humans and other living organisms get from each parent. Half of a person's DNA comes from their mother, and the other half comes from their father.

Your DNA is organized into small parts called genes. Genes act as coded instructions to control how our bodies are built and influence what we look like.

Experts estimate that humans have about 20, to 25, genes. For most genes, one copy is inherited from the biological mother and one copy is inherited from the biological father which we will refer to as simply the "mother" and "father" throughout. The version of each gene that a parent passes down to their child is known as an allele. The traits we end up inheriting from our parents depend on how the alleles interact with each other. Take eye color, for instance. Different combinations of alleles produce brown, blue, green, or hazel eye colors, though the last two are more unique than brown or blue eyes.

Here's are two common scenarios that might occur:. Here's where it can get a little tricky. An allele can be dominant or recessive. Dominant alleles express a trait, even if there is only one copy. Recessive alleles can only express themselves if there are two copies—one from each parent.

And you've probably figured out by now that dominant alleles overrule recessive alleles. Diploid organisms, for example, humans, have paired homologous chromosomes in their somatic cells, and these contain two copies of each gene. An organism in which the two copies of the gene are identical — that is, have the same allele — is called homozygous for that gene. Phenotypes the expressed characteristics associated with a certain allele can sometimes be dominant or recessive, but often they are neither.

A dominant phenotype will be expressed when at least one allele of its associated type is present, whereas a recessive phenotype will only be expressed when both alleles are of its associated type. One exception is incomplete dominance sometimes called blending inheritance when alleles blend their traits in the phenotype. An example of this would be seen if, when crossing Antirrhinums — flowers with incompletely dominant "red" and "white" alleles for petal color — the resulting offspring had pink petals.

Another exception is co-dominance, where both alleles are active and both traits are expressed at the same time; for example, both red and white petals in the same bloom or red and white flowers on the same plant. A person with one "A" blood type allele and one "B" blood type allele would have a blood type of "AB". A wild type allele is an allele which is considered to be "normal" for the organism in question, as opposed to a mutant allele which is usually a relatively new modification.

Note that with the advent of neutral genetic markers, the term 'allele' is now often used to refer to DNA sequence variants in non-functional, or junk DNA.

For example, allele frequency tables are often presented for genetic markers, such as the DYS markers. Also there are many different types of alleles. Reference Terms. An individual's genotype for that gene is the set of alleles it happens to possess.

If a fern plant is heterozygous for a particular trait, how can the alleles that control that trait be described? Krishan T. Jul 15, Explanation: The gene controlling a trait has two alternate alleles.

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