Crossing over that results in genetic recombination in higher organisms occurs between:

Options

A. sister chromatids of a bivalent
B. non-sister chromatids of a bivalent
C. two daughter nuclei
D. two different bivalents

Answer

**Step-by-Step Solution:**

1. **Understanding Crossing Over**:
- Crossing over is a process that occurs during meiosis where homologous chromosomes exchange genetic material. This exchange results in genetic recombination, which increases genetic diversity in offspring.

2. **Identifying Chromatids**:
- In a homologous pair of chromosomes, you have two types of chromatids: sister chromatids and non-sister chromatids. Sister chromatids are identical copies of a single chromosome, while non-sister chromatids are from different homologous chromosomes.

3. **Defining Homologous Chromosomes**:
- Homologous chromosomes are pairs of chromosomes that have the same gene loci but may carry different alleles (variants of a gene). One chromosome is inherited from the mother and the other from the father.

4. **Recognizing the Bivalent Structure**:
- During prophase I of meiosis, homologous chromosomes pair up to form a structure called a bivalent. This is where crossing over occurs between non-sister chromatids.

5. **Identifying the Correct Answer**:
- The crossing over that leads to genetic recombination occurs between non-sister chromatids of a homologous pair of chromosomes. Therefore, the answer to the question is that crossing over occurs between non-sister chromatids.

**Final Answer**: Crossing over that results in genetic recombination in higher organisms occurs between non-sister chromatids of a homologous pair of chromosomes.

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