Question

All living things have cells, and inside those cells are structures called chromosomes.
Chromosomes carry your DNA, which is the set of instructions that tells your body how to
grow, look, and function. A diploid cell has two sets of chromosomes. Most of the cells in
your body, like skin, muscle, and blood cells, are diploid. A haploid cell has only one set of
chromosomes. Haploid cells are used in sexual reproduction, such as sperm and egg cells.
During fertilization, the haploid sperm and haploid egg join together to form a diploid cell,
restoring the normal chromosome number. If gametes were not haploid, the chromosome
number would double each generation, causing major problems. Diploid cells also help
organisms grow, repair injuries, and replace old cells.
Open-Ended Questions
1. Explain in your own words how haploid cells and diploid cells are different. Why
does this difference matter in living organisms?
2. Describe what happens during fertilization and explain why haploid cells are
needed for this process to work correctly.
3. Why would it be a problem if gametes contained two sets of chromosomes instead
of one? Use information from the passage to support your answer.
4. How do diploid cells help your body grow and repair itself? Give an example of a
situation where diploid cell division is important.
5. Based on what you read, explain why keeping the correct chromosome number in
each generation is important for the survival of a species

Answer 1

1. Haploid cells have one set of chromosomes (n) and diploid cells have two sets (2n). This difference matters because diploid cells have two copies of every gene for growth, repair, and normal body functions, while haploid cells are designed to combine during reproduction so the offspring get the correct number of chromosomes.

2. During fertilization a haploid sperm and a haploid egg join to form a single diploid cell (a fertilized egg). Haploid gametes are needed so that when they fuse the resulting cell has the normal two sets of chromosomes; without haploid gametes the chromosome number would not be restored correctly.

3. If gametes contained two sets of chromosomes instead of one, the chromosome number would double with each generation (for example 2n × 2n → 4n, then 8n, etc.). That increasing chromosome number would disrupt the balance of genes and cell functions, causing abnormal development and serious problems for the organism and its offspring.

4. Diploid cells divide by mitosis to make more cells with the same two sets of chromosomes, which lets tissues grow, replace old cells, and repair injuries. Example: when you cut your skin, diploid skin cells divide to produce new skin cells to close and heal the wound.

5. Keeping the correct chromosome number across generations preserves the proper balance of genes needed for normal development, function, and fertility. If chromosome numbers changed unpredictably, offspring could have wrong gene dosages or malfunctioning cells, threatening the survival and health of the species.