write an answer for the following question in the space provided
6. some people have one sickle cell gene and one normal gene. they have few defective cells and no symptoms because the sickle cell gene is recessive. how does the human system of reproduction result in people getting one copy of a sickle cell gene and one copy of a normal gene? describe the process.

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write an answer for the following question in the space provided
6. 	some people have one sickle cell gene and one normal gene. they have few defective cells and no symptoms because the sickle cell gene is recessive. how does the human system of reproduction result in people getting one copy of a sickle cell gene and one copy of a normal gene? describe the process.

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# Brief Explanations:
1. **Parent Genotypes**: One parent has one sickle cell (let's say $ s $) and one normal ( $ S $) gene ($ Ss $), or one parent is a carrier ($ Ss $) and the other has normal genes ($ SS $) but a mutation occurred, or one parent has sickle cell trait ($ Ss $) and the other also has $ Ss $ (but in this case, the offspring can get $ Ss $, $ SS $, or $ ss $). For the case of getting $ Ss $ (one sickle, one normal), let's consider a carrier parent ($ Ss $) and a normal parent ($ SS $) first, or two carriers ($ Ss \times Ss $).
2. **Meiosis in Parents**: During meiosis, the parent's cells (germ cells) undergo cell division to form gametes. For a parent with genotype $ Ss $, the homologous chromosomes with the $ S $ and $ s $ genes separate. So, one gamete will get the $ S $ allele and another will get the $ s $ allele. A parent with $ SS $ will only produce gametes with $ S $, and a parent with $ ss $ (sickle cell disease) will produce gametes with $ s $.
3. **Fertilization**: When fertilization occurs, if one gamete from a carrier parent (with $ s $) fuses with a gamete from a normal parent (with $ S $), the resulting zygote will have genotype $ Ss $. Alternatively, if two carrier parents ($ Ss $) have their gametes fuse, a gamete with $ s $ from one and $ S $ from the other will also result in $ Ss $.
4. **Development**: The zygote with $ Ss $ then develops into an individual with one sickle cell gene ($ s $) and one normal gene ($ S $). The recessive nature of $ s $ means that the dominant $ S $ allele masks the effect of $ s $ in terms of symptoms, but the individual is a carrier.

# Answer:
1. **Parent Genotypes**: One or both parents are carriers (genotype $ Ss $, having one sickle cell gene $ s $ and one normal gene $ S $) or one parent is a carrier ($ Ss $) and the other is normal ($ SS $) with a mutation, or two carriers ($ Ss \times Ss $).
2. **Meiosis**: In carrier parents ($ Ss $), meiosis separates the $ S $ and $ s $ alleles into different gametes (one gamete gets $ S $, another $ s $).
3. **Fertilization**: A gamete with $ s $ (from a carrier or affected parent) fuses with a gamete with $ S $ (from a normal or carrier parent).
4. **Development**: The fertilized zygote ($ Ss $) develops into an individual with one $ s $ (sickle) and one $ S $ (normal) gene, showing few defective cells/symptoms due to $ s $ being recessive.

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