GeneticsLesson 1 of 1 in the course The Cellular Basis of Inheritance

Meiotic Chromosome Variation: Number, Dosage, and Structural Rearrangements

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

Chromosome abnormalities can arise when chromosomes do not separate as they should during meiosis. This lesson introduces karyotypes and explains how nondisjunction can produce cells with too many or too few chromosomes.

Cytogenetics is the study of chromosomes, including their number and structure. A person’s chromosomes can be examined by collecting cells, often white blood cells, and encouraging them to divide. A chemical arrests cell division during metaphase, when chromosomes are condensed and relatively easy to see. The cells are fixed, stained, and viewed under a microscope.

All flashcards

What is X inactivation?
The condensation and silencing of all but one X chromosome in each cell.
What is polyploidy?
Having more than the usual number of complete chromosome sets.
What is an inversion?
A chromosome segment that breaks, rotates 180 degrees, and reinserts.
What is a reciprocal translocation?
An exchange of segments between nonhomologous chromosomes without overall gain or loss of genetic material.
What is nondisjunction?
Failure of homologous chromosomes or sister chromatids to separate correctly during meiosis.

Quiz questions

  1. Which changes can a karyogram reveal?Answer: Extra or missing chromosomes and some large structural changes.
  2. If homologous chromosomes fail to separate in meiosis I, what chromosome distribution occurs among the four resulting gametes?Answer: Two gametes lack that chromosome, and two have two copies.
  3. How does random X inactivation produce cellular mosaics?Answer: Different early embryonic cell lineages inactivate different X chromosomes.
  4. Which statement compares polyploidy in plants and animals?Answer: Polyploidy is common in plants but rare in animals.
  5. What defines a reciprocal translocation?Answer: Two nonhomologous chromosomes exchange segments without overall genetic-material gain or loss.

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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