Genetics Little Lyric H ✓ Solved

Genetics Little Lyric H

Little Lyric has the autosomal recessive disorder of cystic fibrosis. Neither of her parents have the disorder. Explain this phenomena through the process of meiosis (from both her parents), heredity (using Punnett square), through conception to her development and expression of cystic fibrosis in the cells that are affected (the ones that use the mutated gene). Explain how/why that is different than her parents.

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Cystic fibrosis (CF) is a hereditary disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, located on chromosome 7. This disorder is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene—one from each parent—to express the disorder. In the case of Little Lyric, although her parents do not exhibit symptoms of cystic fibrosis, they can still be carriers of the CFTR mutation. Understanding the genetic mechanisms involved requires a careful look at meiosis, heredity, and the subsequent development of cystic fibrosis in Lyric's cells.

Meiosis and Genetic Inheritance

Meiosis is the process by which germ cells (sperm and eggs) are produced. During this process, a single diploid cell (containing two sets of chromosomes) undergoes two rounds of division to produce four haploid cells. Each haploid gamete receives one chromosome from each homologous pair, which includes one copy of each gene. In the case of cystic fibrosis, both parents of Little Lyric could be carriers of one normal allele (C) and one mutated allele (c), denoted as genotype Cc.

During meiosis, these parents can produce gametes with the following genotypes: C (normal allele) or c (mutated allele). When considering the potential combinations of these gametes during fertilization, a Punnett square can be employed to visualize the probabilities of the offspring's genotypes:

Based on this Punnett square, the probabilities of the offspring's genotypes are as follows:

• CC: 25% (not affected)
• Cc: 50% (carriers)
• cc: 25% (affected by cystic fibrosis)

Thus, there is a significant chance (25%) that a child born to two carrier parents will inherit two copies of the mutated allele and be affected by cystic fibrosis, as is the case with Little Lyric.

Conception and Development of Cystic Fibrosis

During conception, one gamete from the father and one from the mother fuse to create a zygote. If the gametes involved are both carrying the mutated allele (c), then the resultant zygote will have the genotype cc, leading to cystic fibrosis. The development of cystic fibrosis impacts various bodily systems, notably the respiratory, digestive, and reproductive systems, primarily due to the malfunctioning of the CFTR protein that regulates salt and water transport across cell membranes.

In Little Lyric's case, her cells expressing the cystic fibrosis phenotype are those that utilize the defective CFTR gene. These include epithelial cells lining the lungs and pancreas. The defective protein leads to thick and sticky mucus buildup, resulting in numerous health issues, including chronic respiratory infections and difficulties in digestion.

Differences Between Parents and Little Lyric

The primary difference between Little Lyric and her parents lies in the expression of the CFTR gene. While her parents have the genotype Cc, they do not show symptoms of the disorder because they have one normal allele (C) that produces enough functional CFTR protein to mitigate the effects of the mutated allele (c). In contrast, Little Lyric's genotype cc means she does not have any functional CFTR protein, resulting in the full expression of cystic fibrosis.

This situation highlights the importance of carrier screening, particularly for genetic disorders like cystic fibrosis. While both parents may be symptom-free, their combination of alleles can lead to the manifestation of the disease in their offspring. Genetic counseling can play a critical role for couples considering having children, helping them understand the risks and implications of being carriers of such autosomal recessive disorders.

Conclusion

Understanding cystic fibrosis through the lens of genetics and inheritance mechanisms illustrates the complexities of genetic disorders. The condition arises not from the parent's overt symptoms but rather from the hidden genetic information passed down through successive generations. In the case of Little Lyric, her journey illustrates the significant implications of being an autosomal recessive disorder carrier and emphasizes the necessity of awareness surrounding genetic health for future generations.

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