Chapter 10.ppt-BB

Carry out the assembly process 2 proteases that

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Unformatted text preview: rry out the assembly process – 2. Proteases that cleave viral capsid proteins BACTERIAL CHROMOSOMES BACTERIAL The bacterial chromosome is found in a region called the The nucleoid nucleoid The nucleoid is not membrane-bounded – So the DNA is in direct contact with the cytoplasm So Bacteria may have one to four identical copies of the same Bacteria chromosome chromosome To fit within the bacterial cell, the chromosomal DNA must To be compacted about a 1000-fold be – This involves the formation of __________ The number of loops varies according to the size of the bacterial The chromosome and the species chromosome DNA supercoiling is a second important way to compact the bacterial chromosome chromosome A schematic illustration of DNA supercoiling schematic Chromosome Function - Influenced by Chromosome DNA Supercoiling DNA The chromosomal DNA in bacteria The is negatively supercoiled is – In E. coli, there is one negative In E. there supercoil per 40 turns of the double helix helix Negative supercoiling has two Negative major effects major – 1. Helps in the compaction of the 1. chromosome chromosome – 2. Creates tension that may be released 2. by DNA strand separation by Upper jaws DNA wraps around the A subunits in a right-handed direction. DNA binds to the lower jaws. Lower jaws A subunits Upper jaws clamp onto DNA. DNA held in lower jaws is cut. DNA held in upper jaws is released and passes downward through the opening in the cut DNA. This process uses 2 ATP molecules. DNA B subunits (a) Molecular mechanism of DNA gyrase function Circular DNA molecule DNA gyrase 2 ATP (b) Overview of DNA gyrase function 2 negative supercoils Cut DNA is ligated back together, and the DNA is released from DNA gyrase. EUKARYOTIC CHROMOSOMES Eukaryotic species contain one or more sets of chromosomes – Each set is composed of several different linear chromosomes The total amount of DNA in eukaryotic species is typically The greater than that in bacterial cells greater Chromosomes in eukaryotes are located in the nucleus Chromosomes nucleus Eukaryotic genomes vary substantially in size In many cases, this variation is not related to complexity of In the species – For example, there is a two fold difference in the size of For the genome in two closely related salamander species the – The difference in the size of the genome is not because of The extra genes extra Rather, the accumulation of ______________. Organization of Eukaryo...
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This document was uploaded on 03/05/2014 for the course CELL 2050 at Tulane.

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