1 Explain why despite of the fact that each mammalian cell h

1. Explain why despite of the fact that each mammalian cell has two alleles for each gene locus, a B cell can only produce antibodies of single antigen specificity.

2. Fill out the accompanying table relating to the properties of IgG molecules and their various parts. Insert a (+) if the molecule or a part exhibits the property, a (-) if it does not, and (+/-) if it does so weekly:

Property

Whole IgG

H chain

L chain

Fab

Binds antigen

Mediates effector function

Has V domains

Has C domains

Property	Whole IgG	H chain	L chain	Fab	Fc
Binds antigen
Mediates effector function
Has V domains
Has C domains

A immature B cell bearing only surface IgM, develops into a cell that simulataneously produces IgM, and IgD and is subsequently capable of switching to the production of IgG, IgA and IgE. It is important to note that each of these heavy chain classes is associated with the same variable heavy chain region (VH) in a given cell and hence bears the same antigen binding specificity. This is because whatever be the heavy chain class of immunoglobulin produced, they will react only to one antigenic determinant since, they all have similar variable regions and therefore similar antigen binding specificity.