03. C - Mouse coat color

Semidominant (incomplete dominance)

intermediate phenotype expressed

Codominant

alleles both expressed in heterozygote

Which chromosome is Nonagouti (a) locus located? What is the coat color for A or a?**

Nonagouti

Chr 2

A or + = agouti (WT); black hair with a subapical yellow band

a = nonagouti (black or brown)

Which chromosome is Brown (b) locus located? What is the coat color for B or b?**

Brown

Chr 4

Tyrp1

Tyrp1^{B or +} = black (WT); Tyrp1^b = brown

Which chromosome is Albino (c) locus located? What is the coat color for C or c?**

Albino

Chr 7

(Tyr)

Tyr^{C or +} = pigmented (WT); Tyr^c = albino

Which chromosome is Dilution (d) locus located? What is the coat color for D or d?**

dilution

Chr 9
(Myo5a)

Myo5a^{D or +} = non-dilute (WT); Myo5a^d = dilute

Which chromosome is P locus located? What is the coat color for P or p?**

Pink-eye dilution

Chr 7

(Oca2)

Oca2^P = black eye (WT); Oca2^p = Pink eye

A vs a: coat color?

Agouti vs nonagouti

dominant to almost all other coat color variants

Tyr+ vs Tyrc : coat color?

WT vs Albino (epistasis expression)

Tyrp1+ vs Tyrp1b : coat color?

WT vs brown

Myo5a+ vs Myo5ad : coat color?

WT vs dilute

Oca2 vs Ova2p : trait color?

pink-eyed dilute

Agouti protein

Melanin productions is under the control of alpha melanocyte stimulating hormone and initiates tyrosinases. Agouti protein binds aMSH and prevents normal signaling and provides different signals that regulate a eumelanin/pheomelanin switch.

The nonagouti allele leads to unrestricted activation of aMSH that leads to ________ fur.

black

The agouti gene determines the relative amount of phaemelanin ____________and eumelanin ______________pigment.

yellow/red; black/brown

Tyrosinase

Melanin pigments are derivatives of tyrosine via the activity of tyrosinase

Agouti allele types:

A: Agouti - "wild type" dominant

a: Nonagouti - removes the banding effect of the agouti gene resulting in one color, usually black

ae : extreme nonagouti - eliminates any yellow strands on the hair resulting in super black mice

Ay: lethal when homozygous, black eyes

Avy: become sooted as the mouse molts, but can be indistinguishable from a lethal yellow; associated with obesity.

Aw: white bellied agouti, white to yellow ventrum; depends on the background of the mouse ... can have a yellow hue!

at: ( MGI website) This allele is particularly interesting because it is recessive to A on the dorsum, but dominant to A on the ventrum. Thus the A/at heterozygote is phenotypically indistinguishable from light-bellied agouti ( Aw/—).

Al: lethal when homozygous.... Will not be able to tell from any other nonagouti when hetero.

AY > Avy > A ~ at > a > ae > al

Agouti Viable Yellow: Avy

Depends on methylation of DNA... can be influenced by diet. The more yellow, the more obesity, diabetes and tumors!

Agouti banding action in mice

The recessive allele (TyrC) produces inactive tyrosinase leading to ___________.

ALBINISM

Homozygosity for TyrC leads to ___________ of all other coat color genes.

EPISTASIS

Recessive Tyrc (cc) causes an inactive form of tyrosinase --> coat color

albino (Recessive (cc) causes masking epistasis of all other coat colors)

Wild type alleles of locus Tyr+ express tyrosinase

melanin (C/-) WT

Albino (Tyrc)

no pigment in hair or eyes. Homozygotes do not perform well on intelligence tests, probably due to visual impairments.

Himalyan (Tyrc-h)

homozygotes are white until the first molt when the ears, tail, nose, and anal region become pigmented. Tyrosinase in these mice are heat labile.

Pink-eyed dilution locus Oca2 (p/p)

results in hypopigmentation of eyes, skin and fur and is associated with oculocutanous albinism type 2 and is linked to Tyr gene.

Both c and p are on chromosome 7

cch/cch

chinchilla (greatly reduced yellow pigment and slightly reduced black pigment)

Why does Himalyan (Tyrc-h) only the dark color on the extremities?

Temperature sensitive!

Mutations at the Myo5a locus will have a lighter hair coat color and ______ defects?

severe neurological defects

Homozygous leaden (ln): coat color

Blue Mice

Piebald tend to have ______ defect in homozygotes

Ednrb+ > Ednrbs

Ednrbs piebald

Homozygotes may develop megacolon

Lyst+ WT Chr 13 "lyst locus"

Lystbg-J

beige

What is the gene for the Black coat color?

Chromosome?

Tyrp1 or Tyrp+: BlackTyrp1b: Brown

Chromosome 4

What is the gene for a pigmented coat color?

Chromosome?

Tyr or Tyr+: Pigmented

Tyrc: Albino (dominant over others) Tyrc-ch: Chinchilla

Chromosome 7

Beige mouse is a model for ??

Chediak-Higashi syndrome

Beige mice are the result of a mutation on which chromosome and lack which cell type?

13; NK cells

Which yellow mouse is viable? Lethal? Phenotype? Model for?

Viable - Ay/a Lethal - Ay/Ay

Phenotype - obese, yellow

Model for - type II diabetes