XY Chromosomes

Sex chromosomes

Chromosomes determining biological sex in organisms.

XY system

Males have XY; females have XX chromosomes.

X0 system

Males have one X chromosome; females have two.

ZW system

Females are ZW; males are ZZ.

Haplo-diploid system

Females from diploid eggs; males from haploid eggs.

Non-chromosomal sex determination

Sex determined by environmental or social factors.

X-linked inheritance

Traits determined by genes on the X chromosome.

Y-linked inheritance

Traits passed from father to son via Y chromosome.

Dominant allele

Completely masks the effect of a recessive allele.

Monogenic traits

Traits controlled by a single gene locus.

Homologous pairs

Chromosomes that are similar in shape and size.

Independent assortment

Genes segregate independently during gamete formation.

Complete dominance

Dominant allele expressed in both homozygous and heterozygous.

Modifier loci

Additional genes affecting the expression of a trait.

Gametes

Reproductive cells carrying alleles for inheritance.

Phenotype

Observable traits resulting from genotype interactions.

Drosophila melanogaster

Model organism for genetic studies; fruit fly.

Color blindness

X-linked trait affecting normal vision; recessive allele.

Carrier female

Female with one normal and one color-blind allele.

SRY gene

Gene on Y chromosome triggering male development.

Parthenogenesis

Asexual reproduction; offspring develop from unfertilized eggs.