Alleles: Difference between revisions
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An allele is the singular term for a form of a [[Gene|gene]] at a certain point of a [[Chromosome|chromosome]]. A different form of a gene has differences in the sequence of [[Nucleotide|nucleotides]] | An allele is the singular term for a form of a [[Gene|gene]] at a certain point of a [[Chromosome|chromosome]]. A different form of a gene has differences in the sequence of [[Nucleotide|nucleotides]]. | ||
Organisms can be [[Haploid|haploid]] or [[Diploid|diploid]]. Haploid organisms have one of each chromosome (and thus only one of a given allele), whereas diploid organisms have two copies of each chromosome and carry two alleles (which may be the same or different). | Organisms can be [[Haploid|haploid]] or [[Diploid|diploid]]. Haploid organisms have one of each chromosome (and thus only one of a given allele), whereas diploid organisms have two copies of each chromosome and carry two alleles (which may be the same or different). | ||
Revision as of 19:29, 30 November 2015
An allele is the singular term for a form of a gene at a certain point of a chromosome. A different form of a gene has differences in the sequence of nucleotides.
Organisms can be haploid or diploid. Haploid organisms have one of each chromosome (and thus only one of a given allele), whereas diploid organisms have two copies of each chromosome and carry two alleles (which may be the same or different).
If the alleles are different in a diploid organism, then the organism is said to be heterozygous for that particular gene. If the alleles are the same, then the organism is said to be homozygous for the gene.
Different alleles can result in changes to the phenotype of an organism, eg. hair colour. Whether a certain allele is recessive, dominant or co-dominant can also affect expression as alleles may interact differently.
If a dominant allele is present then it will be expressed. If a recessive allele is present, the organism must be homozygous for the gene for it to be expressed.