BIOL 200 (Section 921) Lecture # 3, June 21, 2006 • Reading for unit 3 on Interphase nucleus (Lecture 3): ECB 2nd edition, Chap 5 pp. 177-191, Chap 15 pp. 502-506, Chap 17 p. 578, Chap 19 pp 651-2. Good questions: 5-1; 5-4 a, b, c; 5-5; 5-7; 5-10; 5-11; 5-12; 5-13; 5-17. • Learning Objectives: 1. Understand chromatin structure. Explain how proteins and DNA interact to form chromosomes, starting with the 2nm naked DNA molecule. Be able to explain the structure of nucleosomes and the forces stabilizing these structures, then proceed to the, 10 nm fibre, higher order structures, chromosomal loops, euchromatin and heterochromatin. 2. Understand the organization of chromosomes; describe centromere and telomere. 3. Describe the organization of the interphase nucleus, and the transport of macromolecules into and out of the nucleus
BIOL 200 (Section 921) Lecture # 3, June 21, 2006. Reading for unit 3 on Interphase nucleus (Lecture 3): ECB 2nd edition, Chap 5 pp. 177-191, Chap 15 pp. 502-506, Chap 17 p. 578, Chap 19 pp 651-2. Good questions: 5-1; 5-4 a, b, c; 5-5; 5-7; 5-10; 5-11; 5-12; 5-13; 5-17. - PowerPoint PPT Presentation
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BIOL 200 (Section 921)Lecture # 3, June 21, 2006
• Reading for unit 3 on Interphase nucleus (Lecture 3): ECB 2nd edition, Chap 5 pp. 177-191, Chap 15 pp. 502-506, Chap 17 p. 578, Chap 19 pp 651-2. Good questions: 5-1; 5-4 a, b, c; 5-5; 5-7; 5-10; 5-11; 5-12; 5-13; 5-17.
• Learning Objectives:1. Understand chromatin structure. Explain how proteins and DNA
interact to form chromosomes, starting with the 2nm naked DNA molecule. Be able to explain the structure of nucleosomes and the forces stabilizing these structures, then proceed to the, 10 nm fibre, higher order structures, chromosomal loops, euchromatin and heterochromatin.
2. Understand the organization of chromosomes; describe centromere and telomere.
3. Describe the organization of the interphase nucleus, and the transport of macromolecules into and out of the nucleus
Eukaryotic DNA is packaged into chromosomesin plants (Fig. 5-1) and human (Fig. Fig. 5-13)
Knobs show ribosomal RNA encoding DNA (rDNA)
Replication and segregation of chromosomes during cell cycle [Fig. 5-17]
Three DNA sequence elements are needed to produce a eukaryotic chromosome that can be
replicated and segregated [Fig. 5-18]
The bacterial Nucleoid: (A) A bacterial cell with a distinct nucleoid (B) Release of chromosomal
DNA from ruptured bacterial cells[Becker et al. The World of the Cell, 6th ed.]
DNA in mitotic chromosomes is more compact than in interphase chromosomes
The interphase nucleus [Fig. 5-19]
Two types of chromatin
– Euchromatin • diffuse in appearance by EM • relatively uncondensed • contains transcriptionally active genes
– Heterochromatin • condensed in appearance by EM • contains mostly inactive genes • constitutive heterochromatin is permanently
condensed • facultative heterochromatin is specifically
inactivated, and depends on the cell type.
Beads on String (nucleosomes and spacer DNA)
Naked DNA
30 nm Interphase chromatin (packed
nucleosomes)
Fig. 8-10, p.253
ONLY during cell division, chromatin is further packaged
Nucleosomes=
DNA+histone proteins
Fig. 5-24, p.186
Fig. 5-21, p.184
A nucleosome core particle showing DNA tightly wrapped around a histone core
30 nm chromatin fibre
NucleosomesIn beads on a string
Fig. 5-21, p.184
Nucleosomes (basic units of chromatin structure) contain DNA wound around a protein core of eight histone molecules
Gel electrophoresis
Gel electrophoresis
Chromatin remodeling complexes change the nucleosome structure
Interphase nucleus
Nuclear envelope
• Is made up of two lipid bilayer membranes, the inner nuclear membrane and the outer nuclear membrane
• The outer membrane is continuous with the endoplasmic reticulum (ER) membrane
• The space between the inner and outer membranes is known as the perinuclear space.
• The nuclear envelope forms a barrier between the cytoplasm and the nucleus and controls the passage through nuclear pores of macromolecules in and out of the nucleus.
Macromolecular transport into and out of the Nucleus
• Is a unique region within the nucleus • It consists of chromosomal regions containing
the ribosomal RNA transcription units • It is the site of ribosomal RNA synthesis • It is the site of assembly of ribosomes • It consists of a fibrous component (DNA and
RNA transcripts) and a granular region consisting of developing ribosomal subunits.
Nucleoplasm - (inside nucleus, lumen of the nucleus)
• Semifluid matrix
• Made up of extended chromatin (DNA and protein complexes) and non-chromatin proteins (i.e. nuclear matrix, nuclear lamina)
• Its function is to contain the genetic material and serve as a site for DNA replication and for transcription of the genetic material.