Genetics: Dominance, Inheritance Patterns, and X-Linked Traits

Vocabulary practice flashcards covering non-Mendelian inheritance patterns (codominance and incomplete dominance), hair texture Punnett square ratios, autosomal vs. X-linked traits, and chromosomal variations.

Codominance

A pattern of inheritance in which two different alleles are inherited and both alleles are fully, equally, and independently expressed in the phenotype at the same time without blending (e.g., AB blood type or a speckled chicken with both black and white feathers).

Incomplete Dominance

A pattern of inheritance where neither allele is completely dominant, resulting in a blending of traits that produces an intermediate phenotype distinct from either parent (e.g., wavy hair from curly and straight alleles, or pink flowers from red and white parents).

Complete Dominance

A form of inheritance in which one allele completely masks the presence and expression of the other allele in the phenotype.

Autosomal Genes

Genes located on the non-sex chromosomes that are typically inherited equally from both biological parents.

X-Linked Traits

Traits controlled by genes located on sex chromosomes, specifically the X chromosome, which is larger and carries significantly more genes than the Y chromosome.

AMAB Susceptibility to Recessive X-Linked Traits

The heightened likelihood of individuals assigned male at birth ($XY$) to express recessive X-linked conditions because they possess only one X chromosome and lack a second X chromosome to provide a backup copy of the gene.

Carrier Status in AFAB Individuals

The state of an individual assigned female at birth ($XX$) who possesses one recessive allele for an X-linked condition without expressing the phenotype, because a normal allele on the second X chromosome masks it.

Red-Green Color Blindness

An X-linked condition whose gene is located on the X chromosome; it is expressed in an $XY$ individual with a single copy, whereas an $XX$ individual requires two copies to express the condition.

Duchenne Muscular Dystrophy

An X-linked disorder that occurs and expresses more commonly in individuals with $XY$ chromosomes.

Hemophilia

An X-linked disorder caused by an abnormal gene on the X chromosome that is more commonly expressed in $XY$ individuals.

Klinefelter Syndrome

A chromosomal variation in which an individual has an $XXY$ sex chromosome pattern.

Turner Syndrome

A chromosomal variation in which an individual has an $XO$ sex chromosome pattern.

Genetic Testing

A clinical diagnostic tool that enables healthcare professionals to identify specific chromosomal patterns and variations beyond sex assignment at birth, supporting personalized care.

Homozygous Dominant ($HH$) Hair Type

The homozygous dominant genotype that codes for straight hair, accounting for $25\%$ of offspring in a cross between two wavy-haired ($Hh$) individuals.

Heterozygous ($Hh$) Hair Type

The heterozygous genotype that results in an intermediate wavy hair phenotype, accounting for $50\%$ of offspring in a cross between two wavy-haired individuals.

Homozygous Recessive ($hh$) Hair Type

The homozygous recessive genotype that codes for curly hair, accounting for $25\%$ of offspring in a cross between two wavy-haired ($Hh$) individuals.