Recall the structure and occurrence of glycogen

Glycogen is a storage polysaccharide found mainly in animal cells. It is also found in some fungi and yeast.

Check the bonding pattern in glycogen

Glycogen is made of glucose units joined by:

• $\alpha(1\to 4)$ glycosidic bonds in the main chain
• $\alpha(1\to 6)$ glycosidic bonds at branch points

So glycogen is a branched polymer, not a straight-chain polymer.

Evaluate each option

A: It is a straight chain polymer similar to amylose
This is incorrect because glycogen is highly branched, whereas amylose is essentially straight-chain with $\alpha(1\to 4)$ linkages.

B: It is present in animal cells
This is correct. Glycogen is the storage carbohydrate in animals.

C: It is present in some yeast and fungi
This is correct. Glycogen occurs in some fungi and yeast as a reserve food material.

D: Only $\alpha$-linkages are present in the molecule
This is correct because glycogen contains only $\alpha(1\to 4)$ and $\alpha(1\to 6)$ linkages, with no $\beta$-linkages.

Conclusion

The incorrect statement is: $\boxed{\text{A}}$

Comparison with stored correct answer

Stored correct answer = A
Derived answer = A
Hence, they agree.