The Chromosomal Basis of Inheritance — Sex-Linked Traits, Linked Genes, and Genetic Disorders Explained | Chapter 15 of Campbell Biology

Welcome to Last Minute Lecture! This post covers the chromosomal basis of inheritance, connecting Mendel’s laws to the behavior of chromosomes as described in Chapter 15 of Campbell Biology. Discover how genes are located on chromosomes, how sex-linked traits and linked genes are inherited, and how chromosomal alterations can result in genetic disorders. Watch the full video summary below and subscribe for clear, chapter-by-chapter genetics insights!

Introduction: Chromosomes as the Carriers of Genetic Information

The chromosome theory of inheritance links Mendel’s discoveries to chromosome behavior during meiosis, explaining how genes are transmitted from parents to offspring. Chromosomes segregate and assort independently, underlying the patterns of inheritance observed by Mendel.

Sex-Linked Inheritance

• Sex-Linked Genes: Located on the X or Y chromosomes. X-linked traits (like red-green color blindness) are more common in males, while Y-linked genes are passed from father to son.
• Examples: Hemophilia and Duchenne muscular dystrophy are X-linked recessive disorders, more frequently expressed in males due to their single X chromosome.

Linked Genes and Genetic Recombination

• Linked Genes: Genes close together on the same chromosome are often inherited together (genetic linkage).
• Crossing Over: During meiosis, linked genes can be separated, creating recombinant chromosomes and increasing genetic diversity.
• Recombination Frequency: Used to estimate distances between genes on a chromosome (genetic mapping).

Chromosomal Alterations and Human Genetic Disorders

• Aneuploidy: Abnormal chromosome number due to nondisjunction during meiosis (e.g., trisomy 21/Down syndrome, Turner syndrome).
• Polyploidy: More than two chromosome sets, usually in plants.
• Structural Changes: Deletions, duplications, inversions, and translocations can cause genetic disorders (e.g., Cri du Chat syndrome, Philadelphia chromosome).

Genomic Imprinting

• Some genes are expressed differently depending on whether they are inherited from the mother or father (parent-of-origin effect).
• Imprinting can influence development and disease (e.g., Igf2 gene in mice).

Mitochondrial Inheritance

• Mitochondria possess their own DNA, inherited maternally.
• Mitochondrial disorders (e.g., Leber's hereditary optic neuropathy) affect tissues with high energy demands, such as nerves and muscles.

Key Terms and Glossary

• Aneuploidy: Abnormal number of chromosomes.
• Chromosome Theory of Inheritance: Genes are on chromosomes; chromosomes assort independently.
• Crossing Over: Exchange of genetic material between homologous chromosomes.
• Genomic Imprinting: Expression depends on parent of origin.
• Linked Genes: Genes inherited together due to proximity on a chromosome.
• Polyploidy: More than two chromosome sets.
• Sex-Linked Genes: Genes on sex chromosomes (X or Y).
• Y-linked Genes: Genes on the Y chromosome, passed from father to son.

Conclusion: Chromosomes as the Blueprint for Inheritance

Chapter 15 of Campbell Biology ties together Mendelian genetics and chromosomal theory, showing how chromosomes explain inheritance patterns, genetic linkage, and human genetic disorders. For a comprehensive explanation, watch our full video summary and keep learning with Last Minute Lecture.

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