CIE A Level Biology复习笔记16.1.2 Homologous Chromosomes

• In diploid cells there are two complete sets of chromosomes in the nucleus
• Chromosomes have a characteristic shape
  • They have a fixed length
  • The position of the centromere is in a particular location
• These characteristic features allow for each chromosome to be identified in a photomicrograph
• In photomicrographs chromosomes are often grouped into their homologous pairs
• Homologous chromosomes:
  • Carry the same genes in the same positions
  • Are the same shape
• During fertilization a diploid zygote is formed
  • In a zygote one chromosome of each homologous pair comes from the female gamete and the other comes from the male gamete
• Having the same genes in the same order helps homologous chromosomes line up alongside each other during meiosis

Human Karyogram showing homologous chromosomes