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Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement
Klug - Essentials of Genetics 10th Edition
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Non è quello che usi tu?Cambia libro di testo
Capitolo 6, Problema 7

Why do human monosomics most often fail to survive prenatal development?

Guida verificata passo dopo passo
1
Understand that monosomy refers to the condition where an individual has only one copy of a particular chromosome instead of the usual two.
Recognize that chromosomes carry many essential genes, and having only one copy (monosomy) means there is a loss of genetic material, which can disrupt normal development.
Consider the concept of gene dosage, which is the number of copies of a gene present in a cell; proper gene dosage is critical for normal cellular function and development.
Realize that in humans, most autosomal monosomies lead to severe imbalances in gene dosage, causing developmental abnormalities that are usually incompatible with life.
Conclude that because of these severe genetic imbalances, human monosomics typically fail to survive prenatal development, leading to early miscarriage or embryonic lethality.

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Monosomy and Chromosomal Imbalance

Monosomy refers to the loss of one chromosome from a pair, leading to a chromosomal imbalance. This imbalance disrupts the normal dosage of genes, causing developmental abnormalities. In humans, most monosomies are lethal because essential genes are missing, impairing vital biological processes.
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Chromosome Structure

Gene Dosage Sensitivity

Gene dosage sensitivity means that the correct number of gene copies is crucial for normal development. Losing one chromosome reduces gene dosage by half for many genes, which can severely affect cellular function and organismal viability. This sensitivity explains why monosomic embryos often fail to develop properly.
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Prenatal Development and Viability

Prenatal development is a critical period where precise genetic regulation is essential for growth and differentiation. Chromosomal abnormalities like monosomy often disrupt these processes, leading to miscarriage or stillbirth. Only a few monosomies, such as Turner syndrome (monosomy X), are compatible with survival due to unique genetic mechanisms.
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Genetics of Development