2.4 Alternate Inheritance Patterns

x2026-03-28 19:35

Status: #new

Alternate Inheritance Patterns

Co-dominance occurs when the presence of two dominant alleles result in a phenotype that exhibits both traits
Example Cross:

Incomplete Dominance occurs when a heterozygous organism exhibits a unmasked (previously unknown) which differers from that of a homozygous or recessive trait
- Essentially, in a heterozygous organism, it could have a trait completely unrelated to that of its two main traits

Chromosomes are classified either as
- Autosomes: - Non-sex Determining Chromosomes
- Sex Chromosomes - Sex Determining Chromosomes

Most genes on the x-chromosome do not have a corresponding gene on the y-chromosome.
- While male sex is determine typically by the Y chromosome, it is actually from the SRY gene that determines male sex. Hence, it is possible for a XX person to inhibit male traits from the SRY gene, or a XY person to not be a male when they lack the SRY gene
Y-linked traits have not been found n humans, although other species have had these traits
- ie. Male guppies have specific traits to make them attractive to females

Red-Green colour blindness is one of these x-linked traits.
- The wild-type (the normal trait) allele is dominant to a recessive colour-blind allele
- ie.
Heterozygous Females are called carriers as there is a 50% probability that their male offspring will receive a recessive allele and exhibit a disorder/non-normal trait

Sex-limited genes are only expressed in a single gender
ie. Prominent facial hair is in men, but both genders have the genes for it in their DNA

Multiple Genes directed at a trait (Non-Mendellian)
- For example:
- Skin Tone is controlled by at least three different genes

Traits determined by environmental factors
They are not determined by DNA sequence alone
- Whether a gene will turn on or off will be based off its phenotype.
- All genes discussed when epigenetic are assumed to be on.

A epigenetic phenomenon where although there is two alleles inherited of a gene, the phenotype is determined based off the allele inherited from one parent
- These phenotypes can be either maternally or paternally determined.
Honey Bee Colony
- Different environmental conditions affect bee genetics