NON-MENDELIAN

Non-Mendelian Inheritance

Inheritance pattern that doesn't completely follow Mendel's Law of Segregation and Independent Assortment; 3 types: (1) doesn't follow Mendel's laws at all; both genotypic and phenotypic ratios differ, (2) genotypic ratio matches Mendel's expected ratio but phenotypic ratio differs,

Incomplete Dominance

Genotypic ratio follows Mendel's laws but phenotypic ratio differs; heterozygotes show a blended intermediate phenotype distinct from either homozygote (e.g., RR-red x R'R'-white parents both pink, F1 cross gives 1 red : 2 pink : 1 white)

Codominance

Both alleles in a heterozygote are fully and separately expressed (not blended); e.g., AB blood type expresses both A and B antigens simultaneously

Multiple Alleles

A single gene has more than 2 possible alleles in the population, though each individual only inherits 2 (one per parent); e.g., blood type alleles IA, IB, i

Polygenic Inheritance

A single trait is controlled by two or more genes, producing a continuous range of phenotypes; e.g., skin color, height

Human Blood Type: Type A

Genotype AA or Ai; can receive from O or A; can donate to A, AB

Human Blood Type: Type B

Genotype BB or Bi; can receive from O or B; can donate to AB, B

Human Blood Type: Type AB

Genotype IAIB; universal recipient (can receive from A, B, AB, O); can donate to AB only

Human Blood Type: Type O

Genotype ii; can only receive from O; universal donor (can donate to A, B, AB, O)

Sex-linked trait

Trait controlled by a gene located on the X or Y chromosome; usually X-linked

Why males more prone to X-linked recessive disorders

Males only have one X chromosome, so a single recessive allele is expressed with no second X to mask it; females need two copies (homozygous recessive) to express the disorder

Hemophilia

X-linked recessive disorder; lacks sufficient blood-clotting proteins; causes frequent nosebleeds, prolonged bleeding, bleeding into joints/muscles

Color blindness

X-linked recessive disorder affecting ability to differentiate colors; more common in males due to X-linked inheritance (having only one X chromosome)

Hypertrichosis Pinnae Auris

Y-linked trait; causes hairy outer ear; only males can have it; passed father-to-son only

Sex-limited trait

Trait expressed in only one sex even if both sexes carry the gene; e.g., lactation (only females lactate)

Sex-influenced trait

Autosomal trait expressed in both sexes but more frequently/strongly in one sex due to hormonal influence

Pattern baldness

Autosomal sex-influenced trait; more frequently manifested in males; expression influenced by testosterone