Sources of Genetic Variation

Name:

Date:

📚 Part 1: Multiple Choice & Check All

1. Which of the following is NOT a major source of genetic variation in sexually reproducing organisms?

Crossing over

Independent assortment

Mitosis

Random fertilization

2. Check all processes that directly create new combinations of alleles during meiosis:

Crossing over

Independent assortment

DNA replication before cell division

Random fertilization after gamete formation

3. Crossing over (exchange of chromosome segments) occurs during which phase of meiosis?

Metaphase I

Prophase I

Anaphase II

Telophase I

4. In small, isolated populations, which process can cause allele frequencies to change randomly from one generation to the next?

Natural selection

Gene flow

Genetic drift

Horizontal gene transfer

✏️ Part 2: Short Answers & Matching

5. Match each source of variation (left) with its description (right). Draw a line between matching items.

A. Independent assortment

B. Crossing over

C. Mutation

D. Random fertilization

1. New allele appears due to a change in DNA sequence

2. Homologous chromosomes exchange segments during meiosis

3. Gametes combine in countless possible pairs to form a zygote

4. Homolog pairs orient independently at the metaphase plate

6. In 2–3 sentences, explain how meiosis increases genetic variation in offspring.

7. Use evidence to make and defend a one-sentence claim: Describe two inheritable sources of genetic variation and how each can affect a population over generations.

8. Fill in the blank and give a brief example: A change in an organism's DNA sequence is called a ___________. One example of its effect is ________________________.

A change in an organism's DNA sequence is called a ___________. One example of its effect is __________________________________________.

9. Optional drawing: Sketch two homologous chromosomes exchanging segments at a chiasma and label the exchanged parts.