Overview
This lecture provides essential key terms from Chapter 13 of Biology 2e, focused on modern understandings of inheritance and chromosomal concepts.
Chromosome Structure and Number
- Autosomes are chromosomes that are not sex chromosomes.
- Euploid individuals have the correct number of chromosomes for their species.
- Aneuploid individuals have an abnormal chromosome number, including segment deletions and duplications.
- Polyploid refers to individuals with extra sets of chromosomes.
- Monosomy is the loss of one chromosome in an otherwise diploid genotype.
- Trisomy is the duplication of one chromosome in an otherwise diploid genotype.
- Karyotype is a description of an individual's chromosome number and appearance.
- Karyogram is a photographic image of a karyotype.
Chromosomal Behavior and Inheritance
- Chromosomal Theory of Inheritance states chromosomes carry genes and their meiosis behavior explains inheritance patterns.
- Homologous recombination is when homologous chromosomes exchange genetic material during meiosis.
- Parental types are offspring with the same allele combination as their parents.
- Nonparental (recombinant) types are offspring with new allele combinations due to recombination.
- Recombination frequency is the observed average crossover events between two alleles.
Chromosome Structural Changes
- Chromosome inversion is a segment that detaches, rotates 180°, and reinserts.
- Paracentric inversion excludes the centromere.
- Pericentric inversion includes the centromere.
- Translocation occurs when a segment of one chromosome attaches to a different nonhomologous chromosome.
Chromosomal Errors and Phenomena
- Nondisjunction is the failure of chromosome pairs to separate during meiosis, causing abnormal chromosome numbers.
- X inactivation is the process in female embryos where one X chromosome condenses to form a Barr body to balance gene dosage.
Key Terms & Definitions
- Aneuploid — individual with an abnormal number of chromosomes.
- Autosome — any non-sex chromosome.
- Centimorgan (cM) — unit for recombination frequency (0.01).
- Chromosomal Theory of Inheritance — theory that chromosomes carry genes and explain inheritance.
- Chromosome inversion — section of a chromosome detaches, rotates, and reinserts.
- Euploid — individual with the correct chromosome number.
- Homologous recombination — exchange of genetic material between homologous chromosomes.
- Karyogram — photographic image of chromosomes.
- Karyotype — description of chromosome number/appearance.
- Monosomy — loss of one chromosome.
- Nondisjunction — failure of chromosomes to separate in meiosis.
- Nonparental (recombinant) type — progeny with new allele combinations.
- Paracentric inversion — inversion outside the centromere.
- Parental types — progeny with parental allele combinations.
- Pericentric inversion — inversion including the centromere.
- Polyploid — individual with extra sets of chromosomes.
- Recombination frequency — measure of crossover events between alleles.
- Translocation — chromosome segment attaches to another chromosome.
- Trisomy — extra chromosome present.
- X inactivation — inactivation of an X chromosome in female embryos.
Action Items / Next Steps
- Review and memorize these key terms for upcoming assessments on chromosomal inheritance.