BIOL 1107 Notes

Chapter 14 Review

• Mendel's 1st Law (Law of Segregation) occurs in Anaphase I of meiosis I.

• Mendel's 2nd Law (Law of Independent Assortment) occurs in Metaphase I of meiosis I.

• Inheritance patterns: Dominant traits appear in every generation; recessive traits may skip generations.

Chapter 15 Overview

• Topics: Inheritance of Sex Chromosomes, Linked Genes, and Organelles.

  • Sex is genetically determined in humans.

  • Inheritance of sex-linked traits.

  • Distinguishing between sex-linked and autosomal genes.

Sex Chromosomes

• Genes in sex chromosomes are inherited differently in males and females.

• Human sex chromosomes: 50 genes are Y-linked and over 1,000 genes are X-linked.

• Segregation of sex chromosomes results in a 1:1 ratio of XX and XY progeny.

  • Male meiosis yields X-bearing and Y-bearing sperm (1:1 ratio).

  • Female meiosis yields X-bearing eggs only.

Non-Mendelian Inheritance Patterns

• Traits do not always follow Mendelian inheritance:

  • Genes on sex chromosomes exhibit different inheritance.

  • Genes close together on the same chromosome do not assort independently.

  • Mitochondrial and chloroplast DNA have distinct inheritance patterns.