Question

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 method of reproduction in humans result in people getting one copy of a sickle cell gene and one copy of a normal gene? Describe the process

Answer 1

Answer: This process of genetic inheritance through sexual reproduction ensures that individuals can inherit a mix of genes from their parents, including the possibility of receiving one copy of a sickle cell gene and one copy of a normal gene, resulting in the carrier state with few defective cells and no symptoms.

Explanation: Sickle cell gene refers to a genetic variant that causes abnormal hemoglobin and leads to sickle cell disease when inherited from both parents. Normal gene refers to the typical gene variant that does not cause any genetic disorders or abnormalities.

The method of reproduction in humans, known as sexual reproduction, involves the fusion of two gametes (sperm and egg) during fertilization. Each parent contributes one set of chromosomes, including the genes, to their offspring.

When it comes to the sickle cell gene, it is inherited in an autosomal recessive manner. This means that the sickle cell trait (having one sickle cell gene and one normal gene) occurs when an individual receives one sickle cell gene from one parent and one normal gene from the other parent.

To illustrate the process:

1. Each parent has two copies of the gene for hemoglobin, the protein responsible for carrying oxygen in red blood cells.
2. One of the parent's copies has the sickle cell gene (HbS) and the other copy has the normal gene (HbA).
3. The same is true for the other parent, with one sickle cell gene (HbS) and one normal gene (HbA).
4. During reproduction, the parent's sex cells (sperm and egg) are produced through meiosis, a specialized type of cell division.
5. In meiosis, the parent's pairs of chromosomes separate, and the resulting sex cells contain only one copy of each chromosome.
6. Each parent's sex cells randomly combine during fertilization to form a new individual with two sets of chromosomes, one from each parent.
7. As a result, there is a 25% chance that the offspring will receive two sickle cell genes (HbS/HbS) and have sickle cell disease, a 50% chance of receiving one sickle cell gene (HbS/HbA) and being a carrier of the trait, and a 25% chance of receiving two normal genes (HbA/HbA) and not having the trait or disease.

Answer 2

The method of reproduction in humans is sexual reproduction, which involves the fusion of gametes from two parents to form a zygote. Each gamete contains half of the genetic information needed to create a new individual. This means that each parent contributes one copy of each gene to their offspring.

For the gene that causes sickle cell disease, there are two possible versions, or alleles: a normal allele and a sickle cell allele. A person who has one copy of the normal allele and one copy of the sickle cell allele is said to be a carrier of sickle cell disease. They have few defective cells and no symptoms because the normal allele is dominant, meaning that its effects are seen even when only one copy is present.

When two carriers of sickle cell disease have children, each parent gives one copy of their sickle cell allele or their normal allele to their offspring. There are four possible combinations of alleles that their children can inherit: normal/normal, normal/sickle cell, sickle cell/normal, and sickle cell/sickle cell. The first combination results in a child who does not carry the sickle cell allele and does not have the disease. The second and third combinations result in children who are carriers like their parents, with one copy of the sickle cell allele and one copy of the normal allele. The fourth combination results in a child who has two copies of the sickle cell allele and will develop sickle cell disease.