Pedigrees and Sex Determination

Vocabulary flashcards covering pedigree interpretation, autosomal and sex-linked patterns of inheritance, and animal sex-determination mechanisms.

Pedigree

A family tree specific to a given genetic disorder that tracks traits across multiple generations to estimate the probability of offspring inheriting a condition.

Filled-in Shape

A symbol in a pedigree representing an individual who phenotypically exhibits the genetic disorder being tracked.

Wild Type

The normal, non-mutated form of a gene or organism that is more commonly found in nature.

Autosomal Recessive Disorder

The most common class of genetic disorders, requiring an individual to be homozygous recessive to display the phenotype; typically indicated when two unaffected parents have an affected offspring.

Autosomal Dominant Disorder

A mode of inheritance where displaying the phenotype requires only one dominant allele, meaning two affected heterozygous parents can have unaffected offspring.

Cystic Fibrosis

An autosomal recessive genetic disorder caused by a mutation in a cellular pump that leads to a buildup of mucus affecting the lungs, pancreas, and liver.

Huntington's Disease

An autosomal dominant disorder characterized by an onset of symptoms between age $30$ and $50$, allowing the mutated gene to be passed to offspring before the carrier is aware of the disorder.

SRY Gene

A gene located on the Y chromosome that has a major impact on male biological development.

XO System

A sex-determination mechanism, commonly found in insects, where sex is determined by the ratio of X chromosomes (females have two X chromosomes while males have only one).

ZW System

A sex-determination mechanism commonly seen in birds where biological males have two of the same chromosome ($ZZ$) and females have two different chromosomes ($ZW$).

Haplodiploid System

A sex-determination system seen in bees where ploidy determines sex; males develop from unfertilized eggs and are haploid, while females develop from fertilized eggs and are diploid.

Temperature-Dependent Sex Determination

An environmental mechanism seen in American alligators where egg incubation temperatures $7$ to $21$ days after laying determine sex: \text{temperatures} \tle 30^\text{o}\text{C} yield females, \text{temperatures} \tge 34^\text{o}\text{C} yield males, and intermediate temperatures yield both.

Hemizygous

Possessing only a single copy of a gene; typical biological males are hemizygous for all genes situated on the X chromosome.

X-Linked Gene

A gene located exclusively on the X chromosome, which carries over $1{,}000$ genes compared to around $100$ carried on the Y chromosome.

X-Linked Recessive Disorder

A mode of inheritance carried on the X chromosome where unaffected carrier mothers produce a disproportionately high number of affected male offspring due to male hemizygosity.

Hemophilia

An X-linked recessive disorder characterized by the impaired ability of the blood to form clots.

Red-Green Color Blindness

An X-linked recessive trait that is rare in females because they require two mutated alleles to express it, but appears more frequently in males who inherit a single mutated X from their mother.