Question

1. Based on information related to muscle fiber differentiation, briefly describe how a mutation that disrupts the synthesis of myostatin by satellite cells could produce the following phenotype (i.e. a dog with lots of muscle).

2. Based on your understanding of melanocyte differentiation, briefly describe how a mutation that increases the synthesis of a protein that competes with MSH could produce the following phenotype (i.e. a dog lacking dark pigment).

Answer 1

1): Double-muscling is a trait previously described in several mammalian species and is caused by mutation in the Myostatin(MSTN) gene.The dog with lots of muscles which means double musceled phenotype known as the "Bully" whippet.

Individuals with this phenomenon carry two copies of a 2-basepairs deletion in the third exon of MSTN leading to premature stop codon at amino acid 313.

The individual carrying only one copy of the mutation are, on average,more mascular than wild-type individuals and are significantly faster.

These results,highlights the utility of performance-enhancing polymorphism.

2): A mutation in the melanophilin MLPH gene is the cause of color dilution.The two allele associated with dilution are 'D'(dominant full color) and 'd'(recessive dilute).

It takes two recessive(dd) to lighten black pigments to gray or blue and red pigments to cream.

The lack of dark pigment(relatively white color) coat color in dogs is caused by mutation in MITF gene and genetic regulation.

(The black color on the body areas of dogs are caused by cells producing 'cumelanin', a black pigments)