Genetics - Inheritance

Mendel's Law of Segregation: During meiosis, the two alleles of a gene (e.g., $A$ and $a$) separate into different gametes so that each gamete carries only one allele ($n$).

Mendel's Law of Independent Assortment: The alleles of two or more different genes (e.g., $Aa$ and $Bb$) get sorted into gametes independently of one another, provided they are on different chromosomes.

Genotype vs. Phenotype: Genotype refers to the genetic makeup ($AA, Aa, aa$), while phenotype is the observable physical trait (e.g., tall vs. short).

Dominant and Recessive Alleles: Dominant alleles ($A$) mask the effect of recessive alleles ($a$) in a heterozygote ($Aa$). Recessive traits only appear in homozygous recessive individuals ($aa$).

Codominance: Pairs of alleles that both affect the phenotype when present in a heterozygote. Example: $I^A I^B$ results in AB blood type.

Sex-linkage: Genes located on the sex chromosomes ($X$ or $Y$). Traits like hemophilia and red-green color blindness are $X$-linked recessive, denoted as $X^h$ and $X^b$.

Multiple Alleles: Some genes have more than two alleles, such as the ABO blood group system involving $I^A$, $I^B$, and $i$.

Test Cross: Testing a suspected heterozygote ($Aa$) by crossing it with a known homozygous recessive ($aa$).