Sex-Linked Inheritance Flashcards

Vocabulary flashcards covering Chapter 10 Section 4 on sex-linked inheritance, including sex chromosomes, fly eye color crosses, pedigree inheritance patterns, and specific X-linked disorders.

SRY gene

A gene located on the $Y$ chromosome that determines male development by allowing an embryo to respond to testosterone; a broken allele results in female physical development despite having $XY$ chromosomes.

X-linked genes

Genes that are located specifically on the $X$ chromosome, which contains significantly more genes than the $Y$ chromosome.

Wild type (fruit flies)

The normal phenotype in fruit flies, characterized by red eyes, which is dominant over the white-eyed mutation.

Carrier

A female who possesses one copy of a recessive defective allele on an $X$ chromosome masked by a dominant normal allele on her second $X$ chromosome, allowing her to pass the trait to offspring without expressing the condition herself.

X-linked dominant traits

Traits where female children of an affected male parent always inherit the condition, and affected females can transmit the condition to both their male and female offspring.

Y-linked traits

Traits or conditions associated with genes on the $Y$ chromosome that appear exclusively in males and are passed directly to all male offspring.

Red-green color vision deficiency

A common $X$-linked recessive disorder affecting approximately $8\%$ of males, characterized by an inability to distinguish well between red and green colors.

Dystrophin

A protein absent in individuals with Duchenne muscular dystrophy, the lack of which prevents muscles from growing properly and causes them to waste away.

Duchenne muscular dystrophy

A serious $X$-linked recessive condition in which the lack of the protein dystrophin leads to muscle degeneration; experimental therapies inject $100{,}000$ immature muscle cells to achieve a $30\%$ to $40\%$ increase in dystrophin.

Fragile X syndrome

An $X$-linked recessive condition associated with a large number of repeat sequences that cause the tips of the $X$ chromosome to appear connected only by a thin thread.

Syndrome

A medical condition characterized by a broad spectrum of variable symptoms, with severity differing widely among affected individuals or across different features within the same individual.