BIL 250 Lecture Notes - Lecture 12: Sister Chromatids, Nuclear Membrane, Karyotype

• School: University of Miami
• Department: Biology
• Course: BIL 250
• Professor: karenalvarezdelfin

Document Summary

Prokaryotic organisms: two major groups; lack a nuclear envelope and membranous organelles. Nucleoid: unenclosed region where the genetic material is present as a long circular dna molecule that is compacted. Do not have a distinct nucleolus but do contain genes that specify rrna molecules. Chromosomes exist in homologous pairs in diploid organisms. Centromere: constricted region of the chromosome; location establishes the general appearance of each chromosome. All somatic cells derived from members of the same species contain an identical number of chromosomes diploid number (2n) Meiosis converts the diploid number of a chromosome to the haploid number. Following fusion of two gametes, the diploid number is reestablished. Homologous chromosomes: for each chromosome exhibiting a specific length and centromere placement, another exists with identical features. Exceptions: many bacteria and viruses have but one chromosomes; yeasts and molds, and certain plants like bryophytes spend the predominant stage of their lives in a haploid state. Locus: gene sites homologous chromosomes contain identical sites.