This document is a summary of GTS161 study units 1,2 and a small part 3 (for University of Pretoria students) or chapters 2, 3 and part of 4 (for other students) from the textbook Genetics a Conceptual Approach the 6th edition by Benjamin A. Pierce. Contains pictures from textbook and is colorful ...
Study unit 1: Chapter 2 Chromosomes and Cellular Reproduction
Living organisms
Eukaryotes can be divided into Prokaryotes
multicellular or unicellular these organisms are Unicellular
COMPARTMENTALIZED SIMPLE CELLS
where the components are bounded by intracellular with no compartmentalised cells.
Structure membranes. Made up of eubacteria and archaea
HAVE A NUCLEUS defining feature NO NUCLEUS
Nuclear envelope surrounds genetic material Genetic material in close contact with other
And separates DNA from other components. Components.
THIS Property has important consequences for the way in which gene expression is controlled.
Multiple linear DNA molecules Genome Usually one circular DNA molecule
a few bacteria can have more than 1
chromosome.
DNA molecules can also be found in Mitochondria Important bacterial and archaeal genes
.and Chloroplasts Found on plastids
Eukaryotic DNA is closely associated Prokaryotic DNA does not exist in
with histones, to form chromatin and a highly ordered and packed arrangement.
sometimes tightly packed chromosomes. Archaea have some histone proteins.
Histone proteins→=help regulate Bacteria= no histone proteins
accessibility of DNA to enzymes and &
other proteins. and enable DNA to fit into .
nucleus.
Bacteria archaea are similar in cell
structure but some genetic processes in
archaea like transcription are more
similar to eukaryotes.
Viruses are simple structures that neither Prokaryotic nor Eukaryotic
since they do not possess the structure of a cell. They are composed
of an outer protein coat that surrounds a nucleic acid (RNA or DNA)
and can only reproduce in a host cell.
, Cell Reproduction Requires the
following to reproduce
successfully
1. genetic information must be copied,
2. the copies of genetic information must be
separated from each other,
3. •the cell must divide.
Prokaryotic Cell Reproduction
• Prokaryotic cells reproduce through the
process of binary fission.
• Replication usually begins at a specific
place on the circular chromosome =
origin of replication
• Simple division: separation of replicated
circular chromosome.
• High rate of replication. Under optimal
conditions: some bacterial cells can divide
every 20 minutes.
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