Hereditary cyanobacteria reproduce asexually by
(a) Single stranded DNA
(b) Double stranded DNA
(c) Single stranded RNA
(d) Double stranded RNA

Options

A. Single stranded DNA
B. Double stranded DNA
C. Single stranded RNA
D. Double stranded RNA.

Answer

To answer the question regarding how hereditary cyanobacteria reproduce asexually, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: We need to determine the type of genetic material that hereditary cyanobacteria use for asexual reproduction.

2. **Identify Cyanobacteria Characteristics**: Cyanobacteria are prokaryotic organisms that can be unicellular, colonial, or filamentous. They lack a true nucleus and have their genetic material organized differently compared to eukaryotic cells.

3. **Types of Asexual Reproduction**:
- Unicellular and colonial cyanobacteria reproduce primarily through binary fission.
- Filamentous cyanobacteria reproduce through fragmentation and spore formation.

4. **Examine Genetic Material**: The genetic material in cyanobacteria is crucial for reproduction. Unlike eukaryotes, cyanobacteria do not have linear chromosomes but instead possess circular DNA.

5. **Determine the Structure of DNA**: The genetic material in cyanobacteria is double-stranded DNA, which is circular in structure. This is essential for the replication process during asexual reproduction.

6. **Evaluate the Options**:
- (a) Single stranded DNA: Incorrect, as cyanobacteria do not use single-stranded DNA for reproduction.
- (b) Double stranded DNA: Correct, as cyanobacteria reproduce using double-stranded circular DNA.
- (c) Single stranded RNA: Incorrect, as this is not the genetic material used for reproduction in cyanobacteria.
- (d) Double stranded RNA: Incorrect, as cyanobacteria do not utilize double-stranded RNA for reproduction.

7. **Conclusion**: Based on the above analysis, the correct answer is (b) Double stranded DNA.

### Final Answer:
Hereditary cyanobacteria reproduce asexually by **(b) Double stranded DNA**.