ೃ⁀➷ 𝐒𝐜𝐢𝐞𝐧𝐜𝐞: 𝐍𝐨𝐧-𝐦𝐞𝐧𝐝𝐚𝐥𝐢𝐚𝐧 𝐆𝐞𝐧𝐞𝐭𝐢𝐜𝐬

Incomplete and Codominance 

Incomplete dominance — Both alleles are partially expressed in an intermediate phenotype. Neither trait is completely dominant, resulting in a blended phenotype. 

Codominance — both alleles of a trait are equally expressed. 

→ black cow (BB) x white cow (WW) = spotted cow (BW)

Multiple Alleles

When more than 2 varieties exists in a trait.

→ Blood group (ABO) in human

→ Coat color in rabbit 

→ coat color in mice 

→ eye color

Human blood type

→ “I” stands for isoagglutinogen (antigen)

→ It is a protein produced by plasma and has a role in your immune system 

→ Antigen triggers your immune system through detection of foreign germs

→ Antibody directly kills or destroys foreign germs

Epistasis 

epistasis occurs when the action of one gene is modified by one or several other genes, which are sometimes called modifier genes. A gene can either mask or modify the phenotype controlled by the other gene.

An interaction between the products of two genes in which one of the genes modify the phenotypic expression produced by the other.

“Epistasis” is a word composed of Greek roots that mean “standing upon.” The gene that does the masking or modifying is called epistatic, while the gene that is masked or modified is called

hypostatic.

modifying epistasis occurs when a gene at one locus modifies or changes the expression of the phenotype of a gene at the second locus. The gene that does the masking or modifying is called epistatic, while the gene that is masked or modified is referred to as hypostatic.

Sex-linked Trait

→ Genes for some traits are found on the sex chromosomes (X or Y)

→ Most of these traits are recessive the normal gene is dominant

→ Heterozygous Females (XXc) are carriers. They do not show the trait, but carry a gene for the trait.

→ Homozygous Females (XcXc) have the trait

→ Males with the gene (XcY) have the trait. —They do not have another X to counterbalance the affected gene

→ Color blindness — The inability to distinguish other colors under normal lighting conditions.

→ Hemophilia — It is a hereditary condition wherein blood fails to clot due to the absence of protein in blood called fibrin (protein involved in blood clotting.) Typically given to sons by their mothers; females are typically only carriers of hemophilia. 

Sex-Influenced Trait

→ Autosomal traits that are influenced by sex.

→ An example is baldness pattern

→ The baldness gene is found only on the X chromosome.

→ Baldness is influenced by hormones such as testosterone and dihydrotestosterone.