Polygenic inheritance

22 important questions on Polygenic inheritance

Where are cutaneous melanocytes located?

In the hair and skin.

Where are the extracutaneous melanocytes located?

In the eye and cochlea.

What four types of melanosome transport are there?

Cytophagocytosis, membrane fusion, shedding-phagocytosis and exocytosis-endocytosis.
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What are the main roles of melanin?

Pigmentation and defense against ultraviolet radiation and mechano-stress.

How does c-Kit play a role in melanocyte survival and proliferation?

Keratinocytes produce SCF, which binds to c-Kit on melanocytes. This activates signaling that promotes survival, proliferation and migration.

How does c-Kit regulate melanin production?

It activates key transcription factors (like MITF).

How does c-Kit help to respond to UV radiation?

By increasing pigment production.

What is caused by dominant c-Kit nonsense variants?

Piebalism.

By what mutation is red hair caused?

A MC1R frameshift mutation.

How does a hair colour get distributed?

Melanocytes give melanosomes to the hair cell that are then distributed through the cell.

How does melanin help with the defense against UV damage?

It forms a protective cap over the nucleus, shielding the DNA.

What does the MC1R gene control?

It controls the production of eumelanin and pheomelanin, the two types of melanin.

What does a high concentration of melanin in the iris result in?

Darker coloured eyes.

What does a low concentration of melanin in the iris result in?

Lighter coloured eyes.

What is a key characteristic of Waardenburg syndrome?

Heterochromia eyes

What disease is caused by MYO5A recessive nonsense mutations?

Type 1 grisecelli syndrome

What is a characteristic of grisecelli syndrome?

Albinism.

What is a characteristic of piebaldism?

Patches of white skin and hair.

How is Waardenburg syndrom inherited?

Autosomal dominant.

How is piebaldism inherited?

Autosomal dominant.

How is Grisecelli inherited?

Autosomal recessive.

How can Waardenburg syndrome cause deafness?

The stria vascularis cells in the cochlea are also melanocytes.

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