Sex-Linked Inheritance

Sex-linked Genes

Genes that are found on sex chromosomes

X-linked

genes found on the X chromosome are called

Y-linked

genes found on the Y chromosome

Z-linked

Sex chromosomes for fowls

X-linked Recessive Genes

Recessive alleles located on the X chromosome

X^a 

X-linked Recessive Genes (trait) is expressed as

carriers

females with both dominant and recessive alleles do not express the trait but are

Hemophilia

bleeding disorder that slows the blood clotting process due to the absence of a blood clotting factor

factor VIII or factor IX

Blood clotting factors for hemophilia

Hemophilia, Red-green colorblindness, Duchenne Muscular Dystrophy

X-linked Recessive Traits

Red-green colorblindness

prevents an individual to perceive the colors red and green

Duchenne muscular dystrophy

progressive muscular disorder that leads to an irreversible gradual wasting of skeletal muscles

X-linked Dominant Genes

• dominant alleles located on the X chromosome

• as long as the dominant allele is present, the trait will be expressed

X^A

X-linked Dominant Gene trait is expressed as

Incontinentia pigmenti

• rare genetic condition that causes abnormalities in the skin, teeth, and eyes.

Fragile X Syndrome, Incontitnentia pigmenti and X-linked hypophosphatemia

Other X-linked Dominant Traits Diseases

Fragile X Syndrome

mutation on the X chromosome that results in mental retardation

X-linked hypophosphatemia

form of vitamin D deficiency or rickets affecting the bones, causing pain, abnormal shape, and osteoarthritis.

Holandric genes

some genes are exclusively found in the Y chromosome and are called

Amelogenesis imperfecta

congenital disorder affecting the formation of the teeth enamel making affected individuals at higher risk for dental cavities and related problems.

autosomal genes

Sex-influenced traits are governed by ________, hence are present in both sexes.

Male-pattern baldness and sheep horn

Sex-influenced Male Dominant Traits

Herbeden’s nodes

Sex-influenced Female Dominant Traits

heterogametic sex

Animals with two different sex chromosomes are of _________ and produce two types of gametes.

homogametic sex

Those with the same sex chromosomes are of ________ and produce only one type of gametes

ZZ-ZW Mechanism

This mechanism of sex determination is exhibited by fishes, amphibians, reptiles, and birds.

temperature

Environmental factors, especially ________ can sometimes play an important role in sex determination