MLB 111 Unit 4 summary and practice questions

MLB 111 UNIT 4
STUDY UNIT 4: THE CELL CYCLE AND CELL DIVISION (5 lectures)
STUDY MATERIAL: Hillis et al., parts of Chapter 11 (see core concepts below).
Lecturer: Dr Markus Wilken
Core Concepts:
● Section 11.1 All cells derive from other cells
● Section 11.2 The Eukaryotic cell division cycle is regulated
● Section 11.3 Eukaryotic cells divide by mitosis
● Section 11.6 Cell death is important in living organisms
● Section 11.7 Unregulated cell division can lead to cancer


LEARNING OUTCOMES:
You have mastered this study theme when you can:
1. Briefly describe the four main events of cell division.
4 main events that define cell division:
• Cell signal
◦ initiate cell division
◦ control when it happens
• DNA replication
◦ copying DNA
◦ so that each of the 2 new cells will have a full complement of genetic information
• DNA segregation
◦ replicated DNA to be distributed appropriately so each receives copy of each
chromosome (separating the DNA)
• Cytokinesis
◦ separating the cell

2. Describe bacterial cell division by referring to the process of binary fission and the role
of the ori and ter in the process.
Prokaryotes (Bacteria) - DNA is not in nucleus.
• Not many organelles so not as many steps in DNA replication.
Eukaryotic cells more complex - DNA in nucleus; organelles etc. There are then more steps.
Different in size - much larger than prokaryotes. (*check)

Prokaryotic cell division - binary fission
• results in reproduction of entire single-celled organism




1

, • cell division signals are usually external factors like nutrient
concentration/environmental conditions
• most have 1 chromosome (circular, folded), a single molecule of DNA
• 2 important regions:
◦ Ori - where replication starts (origin)
◦ Ter - where replication ends (terminus)
◦ Means it always starts in same place and ends in same place.
• Prokaryotic DNA segregation
◦ after replication, ori regions move to opposite ends of cell
◦ segregates daughter chromosomes
• Prokaryotic cytokinesis
◦ cell membrane pinches in; protein fibers form a ring
◦ new cell wall materials are synthesised, resulting in separation of the two cells




3. Completely name and describe the different phases of the eukaryotic cell cycle
(Interphase consisting of G1, S, and G2, and M-phase).
Eukaryotes



2

, • Although cells are ready to divide, they may not.
• Cell division signals are related to the needs of the entire organism
• Eukaryotic DNA replication is more complex
◦ Eukaryotes have more than one chromosome, which is in the nucleus
◦ Replication starts at many origins on the chromosome
◦ Replication is limited to one part of the cell cycle
• Eukaryotic DNA segregation
◦ Mitosis - separates the newly replicated chromosomes into two new nuclei
◦ one copy of each chromosome ends up in each daughter cell
• Eukaryotic cytokinesis
◦ proceeds differently in animal and plant cells (plants have cell walls)




All cells come from pre-existing cells
• same 4 steps common to all cell division
• Eukaryotic cell division needs more regulation bc more complex *slideshow

Have to be able to draw, interpret, and understand cell cycle.
Cell cycle
• Phases a cell passes through to produce daughter cells by cell division
Interphase
• prepares cell for division.
• Has 3 subphases (G1, S, G2)
• duration is highly variable
• nucleus is visible and cell functions occur
• G1:




3