- The Order Of Genes In The Wild Type 2 Phage Virion Linear Genome Is Cos A B C D E Att Int Xis N C O P Q S R Cos Cos A 1 (257.39 KiB) Viewed 139 times
The order of genes in the wild type 2 phage virion (linear genome) is Cos-A B C D E att int xis N c O P Q S R-Cos COS A B C D E att int xis N c O POSR Cos 2. phage genome gal att bio Bacterial genome Figure 1: Positions of Cos and att sites and of phage and bacterial genes. 1) The genome of E coli contains a single site (att) where a 2 phage can integrate its genome. After integration, how many att sites are found in the bacterial genome? Briefly explain. (6 pts) 2) Given that the bacterial attachment site, att, is between the gal and bio genes on the bacterial chromosome, what is the gene order in the prophage (phage integrated inside the bacterial chromosome). Include the position of the bacterial gal and bio genes. You do not need to draw a diagram. Simply list the genes in the correct order (8 pts). 3) A new phage is discovered whose gene orders is identical in the virion and in the prophage. What does it say about the location of the att site with respect to the termini of the linear phage genome? (6 pts) 4) A wild type 2 lysogen is a bacterium whose genome contains a wild-type copy of the 2 prophage (Cos-A BC DE att F G H-Cos). This lysogen is infected with another 2-phage carrying a gene Z located between E and att (Cos-A B C D E Z att F G H-Cos). The superinfection gives rise to a rare, doubly lysogenic bacteria that carry both the wild type 1 and the 2-Z prophage. Assuming the second phage (2-2) also enter the bacterial chromosome at an att site, what are the two possible orders of the bacteriophage genes in the bacterial genome? Indicate the location of the bacterial gal and bio genes. You do not need to draw a diagram. Simply list the genes in the correct order (8 pts). 5) In the 2 lysogen bacteria, the RecA gene is upregulated when an inducer is added to a bacterial liquid culture. A few hours after the addition of the inducer the absorbance at 600 nm of the liquid culture (turbidity) decreases sharply. a) Why is the turbidity of a bacterial liquid culture measured? (4 pts) b) Explain why the upregulation of RecA leads to a decrease of turbidity (6 pts).