At least _____ genes must interact to produce a trait.
The least number is 2, however this is very rare. Most traits require many genes to produce a trait.
It depends on the trait. Some are Mendelian traits where there is one dominant and one recessive allele. Some traits are governed by multiple alleles, like blood groups, and some traits are governed by polygenic inheritance where several sets of genes determine the trait, like height in humans.
They are located on one chromosome.
Polygenic inheritance occurs when one characteristic is controlled by two or more genes. Often the genes are large in quantity but small in effect. Examples of human polygenic inheritance are height, skin color, eye color and weight. Polygenes exist in other organisms, as well.
It was once believed that one gene controls one trait, so it is possible. Currently, the belief is that one gene can interact with other genes to control a trait, and that one gene can control more than one trait.
A dominant trait is expressed when two different genes for the same trait are present.
the number of genes that usually determine a trait
These are Genes that present in the chromosomes shows intergenic interaction. These genes located in 2 loci controlling the same trait and interact to produce some totally new traits or phenotypes that neither of the genes alone can produce the inheritance. Eg: Comb pattern in Poultry [9:3:3:1] The genes involved are RRpp for Rose Comb and rrPP for Pea Comb. These interact and modify the single comb, basic type of comb pattern to walnut type. The Progenies Phenotypes are Walnut Comb = 9 Rose Cob = 3 Pea Comb = 3 Single Comb = 1
A trait controlled by many genes
If the two different genes include one dominant allele and one recessive allele, which is the heterozygous genotype, the dominant phenotype is expressed. For example, if R represents the red flower allele and r represents the white flower allele, the flowers would be red. If the trait is governed by incomplete dominance, then the heterozygous genotype (Rr) will produce an intermediate phenotype, such as pink.