2002 Biology Frq

2002 FRQ

1(a) Based on this graph it is possible to observe that the bacteria experienced exponential growth up until the introduction of bacteria phages. Once this virus was introduced the bacteria heavily declined while the virus began its exponential increase. As time went on he bacteria began to fight back and started to overcome the virus and began reproducing again, elevating their numbers. After the bacteria “fought back” the viruses began reproducing in non resistant cells and that is why they appear to have entered a co-inhabitance state.

1(b) The infection cycle of a DNA virus begins with the attachment to a particular host cell by the membrane or cell wall. After the virus is attached it will penetrate the cell and inject its DNA. Once inside the synthesis of important components will begin in order to later form the new cell. Once all the components are made or retrieved the new viral cell is formed and the virus will then burst out of the cell killing it. However the virus can leave the cell and encase its self in the host cells membrane to disguise itself. 1(c) A retrovirus can become part of the host cells genome in many ways. First off a retrovirus is an RNA virus that utilizes an enzyme known as transcriptase. Transcriptase allows these retroviruses to reverse copy a DNA template. This means that is can change a single strand of RNA into a double strand of DNA. This enzyme helps with the enzymatic incorporation into the host cells genome just like it does with ligase.