MOL-BIO LEC MIDTERMS (Sex Inheritance)

Holandric Genes

Genes located on the nonhomologous region of the Y chromosome, inherited exclusively through male descent.

Sex-Linked Genes

Genes located on the X chromosome, often associated with traits like color blindness and sickle cell anemia.

X-linked Recessive

More common in males; affected males do not pass the trait to sons but can pass it to daughters (carriers)

X-linked Dominant

Affected males pass the trait to all daughters but no sons; affected females pass it to ~50% of offspring.

Sex-Limited Genes

Genes present in both sexes but expressed in only one (e.g., beard growth in males, milk production in females).

Sex-Influenced Traits

Autosomal traits whose expression differs by sex (e.g., male pattern baldness requires one recessive allele in males but two in females).

XX

Female Sex Chromosomes

XY

Males Sex chromosomes

47, XXX (Trisomy X)

Females with an extra X chromosome.

47, XXY (Klinefelter Syndrome)

Males with an extra X chromosome.

47, XYY (Double Y Syndrome)

Males with an extra Y chromosome.

45, X0 (Turner Syndrome)

Females missing one X chromosome.

Hemizygous

A condition where males (XY) have only one allele for X-linked genes (no counterpart on Y).

Sexual Dimorphism

Physical differences between sexes (e.g., size, coloration) influenced by sex-limited genes.