Which of the following processes/techniques can be included under biotechnology ?
(i) In vitro fertilisation
(ii) Synthesis of a gene
(iii) Correcting a defective gene
(iv) Developing a DNA vaccine

Options

A. (i) and (ii)
B. (ii) and (iii)
C. (iii) and (iv)
D. (i),(ii),(iii) and (iv)

Explanation

To determine which processes or techniques can be included under biotechnology, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Biotechnology**:
- Biotechnology involves the use of living organisms, cells, and biological systems to develop products and processes that benefit humanity. This includes techniques that utilize microorganisms, plant cells, animal cells, and enzymes.

2. **Evaluating Each Option**:
- **(i) In vitro fertilization**: This is a process where an egg is fertilized by sperm outside the body. It is a technique used in reproductive technology and is considered a biotechnological method since it involves manipulating biological systems to achieve a desired outcome.

- **(ii) Synthesis of a gene**: This refers to the artificial creation of a gene using chemical processes. This is a fundamental aspect of biotechnology as it involves genetic engineering and manipulation of DNA, which is a core component of biotechnological applications.

- **(iii) Correcting a defective gene**: This process, often referred to as gene therapy, involves repairing or replacing defective genes to treat genetic disorders. It is a significant application of biotechnology, focusing on genetic modification to improve health outcomes.

- **(iv) Developing a DNA vaccine**: This involves using a piece of genetic material from a pathogen to stimulate an immune response. DNA vaccines are a modern approach to vaccination and are firmly rooted in biotechnological principles.

3. **Conclusion**:
- All four options listed (i, ii, iii, iv) are processes or techniques that fall under the umbrella of biotechnology. Therefore, the correct answer is that all these processes can be included under biotechnology.

### Final Answer:
All of the following processes can be included under biotechnology:
- (i) In vitro fertilization
- (ii) Synthesis of a gene
- (iii) Correcting a defective gene
- (iv) Developing a DNA vaccine

Thus, the correct option is **D: 1st, 2nd, 3rd, and 4th**.

---