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Modern Understandings of Inheritance

Modern Understandings of Inheritance

A color micrograph of dye-stained chromosomes glowing green and orange against a dark background: one long, thin, banded strand extends to the upper left, while the rest coil into a dense tangle of thicker banded strands at the lower right, beside a 25 µm scale bar.
Chromosomes are threadlike nuclear structures consisting of DNA and proteins that serve as the repositories for genetic information. The chromosomes depicted here were isolated from a fruit fly’s salivary gland, stained with dye, and visualized under a microscope. Akin to miniature bar codes, chromosomes absorb different dyes to produce characteristic banding patterns, which allows for their routine identification. (credit: modification of work by “LPLT”/Wikimedia Commons; scale-bar data from Matt Russell)

The gene is the physical unit of inheritance, and genes are arranged in a linear order on chromosomes. Chromosome behavior and interaction during meiosis explain, at a cellular level, inheritance patterns that we observe in populations. Genetic disorders involving alterations in chromosome number or structure may have dramatic effects and can prevent a fertilized egg from developing.

Sections

  • Chromosomal Theory and Genetic Linkage — Sutton’s Chromosomal Theory of Inheritance, genetic linkage, how homologous recombination (crossing over) works, chromosome mapping, and calculating gene distances with a three-point test cross.
  • Chromosomal Basis of Inherited Disorders — how a karyogram is created, how nondisjunction leads to disorders in chromosome number, the disorders aneuploidy causes, and how inversions and translocations produce errors in chromosome structure.

This chapter is adapted from Biology 2e, Chapter 13: Modern Understandings of Inheritance by Mary Ann Clark, Jung Choi, Matthew Douglas, and OpenStax, © OpenStax, licensed under CC BY-NC-SA 4.0. Access the original for free at openstax.org. Each section page records its own changes from the source. Changes: the chapter-opening micrograph is the source’s, re-encoded for the web with its credit kept in the caption; its alt text is rewritten from the image, because the source alt calls the picture an electron micrograph while the image is a color, dye-stained light micrograph and the caption itself says the chromosomes were stained with dye and visualized under a microscope — reported as a source defect.

Laws of InheritanceChromosomal Theory and Genetic Linkage