Synapsis (pairing of homologous chromosomes) and crossing over occur only in germ line cells.

Answer

To determine whether the statement "Synapsis (pairing of homologous chromosomes) and crossing over occur only in germ line cells" is true or false, we can break down the concepts involved:

### Step 1: Define Synapsis
- Synapsis is the process where homologous chromosomes pair up during meiosis. This occurs during prophase I of meiosis, where each chromosome aligns with its homologous partner.

**Hint:** Remember that synapsis is specific to meiosis and involves the pairing of homologous chromosomes.

### Step 2: Understand Crossing Over
- Crossing over is the exchange of genetic material between homologous chromosomes during synapsis. This process increases genetic diversity in the resulting gametes.

**Hint:** Think about how crossing over contributes to genetic variation in offspring.

### Step 3: Identify Where These Processes Occur
- Both synapsis and crossing over occur exclusively during meiosis, which takes place in germ line cells (the cells that give rise to gametes such as sperm and eggs).

**Hint:** Consider the distinction between germ line cells and somatic cells when thinking about where meiosis occurs.

### Step 4: Compare with Mitosis
- In contrast, mitosis does not involve synapsis or crossing over because it is a process of cell division that produces identical daughter cells, and homologous chromosomes do not pair.

**Hint:** Recall that mitosis is for growth and repair, while meiosis is for producing gametes.

### Step 5: Conclusion
- Since synapsis and crossing over are processes that occur only in germ line cells during meiosis, the statement is **true**.

**Final Answer:** The statement "Synapsis (pairing of homologous chromosomes) and crossing over occur only in germ line cells" is **true**.