For Some Single Gene Disorders, Some Members of a Family

question 23

Essay

For some single gene disorders, some members of a family who have the same genetic variants at the disease locus as strongly affected family members either show a much milder phenotype or no disease symptoms. List five explanations for why there can be a lack of penetrance or variable expressivity of a single gene disorder.

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Definitions:

Cytokine

Protein or peptide secreted by a cell that regulates the activity of neighboring cells.

Lymphocyte Proliferation

The rapid increase or multiplication of lymphocytes, a type of white blood cell, often in response to infection or disease.

Helper T Cells

A type of T cell that plays a central role in the immune response, helping to activate and direct other immune cells.

Macrophages

Large white blood cells that engulf and digest cellular debris, foreign substances, microbes, and cancer cells in a process called phagocytosis.