Recessive gene refers to such a geneAlleleOnly when the gene is homozygous will the determined trait be expressed.In the heterozygous state, the phenotype of the organism showsDominant geneDetermined characteristics.
Generally, recessive genes are represented by lower case letters, while dominant genes are represented by upper case letters.So, if the genedominant homozygote Expressed as AA, the recessive homozygote is expressed as aa,HeterozygoteIt is expressed as Aa.
staygeneticsIn, recessive gene means that when an individual isHomozygousA gene that can express only the traits determined by the gene when recessive[1]。If it isHeterozygote, it shows the phenotype determined by the dominant gene.
according tomendelian inheritance If a heterozygous individual carrying the recessive gene propagates with another heterozygous individual carrying the same recessive gene, the probability of producing homozygous recessive offspring is 25%.
Examples of recessive genes, such as the blue color of eyes, are recessive relative to the brown color of eyes;There is also the wrinkle phenotype of peas, which is equivalent to the wrinkle free peas. It is also recessive[1]。
Genetic relationship
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Homozygous genes are either double dominant or double recessive.If upper case letters are used to indicate dominance and lower case letters are used to indicate recessiveness, then homozygote of AA combination isdominant homozygote , and the aa combination isRecessive homozygote, and Aa, a combination of uppercase and lowercase, is a heterozygote.The traits shown by heterozygotes are determined by dominant genes, which is the "priority" of dominant genes.
A typical example of recessive inheritance is the inheritance of pea seed shape.Peas can be round and smooth (related to allele R) or wrinkled (related to allele r).There are three combinations of alleles, namely genotype RR, Rr and rr.RR (homozygote) individuals are round smooth peas, while rr (homozygote) individuals are wrinkled peas.In Rr (heterozygote) individuals, the R allele conceals the existence of the r allele, so these individuals are also round smooth peas.Therefore, allele r and allele R are recessive.
