AP BIO UNIT 6 FRQ

(d) Referring to Figure 1B, explain why any newly synthesized strand of DNA is the result of both continuous and discontinuous DNA synthesis.

The DNA polymerase is the enzyme which copies in the direction of 5' to 3' in the leading strand and in case of lagging stand it is opposite. that is from the 3' to 5'. Replication in the 3' to 5' takes place in the fragments which is laid by the Okazaki fragments. These small fragments are kept together by the help of the enzyme known as DNA Ligase. So, called as discontinues. Incase of leading strand, the strand is in the same direction of the for the process of replication (5' to 3'). So it is continuous. Hence, the whole process is a combination of continuous and discontinuous DNA synthesis.

(b) Identify the independent variable in the experiment described. Identify the plasmid that was used as a negative control for luciferase activity. Justify including the plasmid with the non-CD3γ active promoter in the experiments.

The aim of the experiment is to analyse regulatory sequences present upstream of the CD3γ gene that might influence the expression of the gene. To do this, they took a plasmid with a luciferase gene present. They then inserted sequences of varying length in the plasmid upstream of the luciferase genes. They then inserted this plasmid into T cells and performed luciferase assays to assess how highly expressed the luciferase gene was from the different regulatory sequences. This would be a good indication of the regulatory activity of that sequence. The only variable that changes throughout the experiment is the regulatory sequence that is inserted upstream of the luciferase gene. This means researchers can determine the effect of that regulatory sequence on the expression of a gene, without the influence of other factors. The plasmid used as a negative control is one that we expect not produce any luciferase activity. In this case, it is the parent plasmid, which does not have an upstream promoter/regulatory sequence, so it will not be able to be expressed, and the assay will detect no (or very little) luciferase activity. This is shown in the attached figure 2. This controls for expression of luciferase not produced by the promoter. The plasmid with the non-CD3 active promoter shows the "normal" activity of the luciferase gene. This controls for the possibility that the inserted sequences do not positively affect gene expression. If this happened and we did not have our control, we wouldn't know if the assay is working properly or whether this sequence just doesn't act as a promoter. Therefore, the non-CD3 active promoter shows us that the luciferase assay is working as expected, and we can therefore judge any changes in expression caused by our regulatory sequence.

(b) Explain why DNA replication cannot proceed to the regions of the chromosome labeled as I in Figure 1B unless topoisomerase binds ahead of each advancing replication fork in region II.

Because replication only follows single strands, not double strands, of DNA. As you can see in the figure, the regions of the chromosome marked as I are on a double strand of DNA and replication proceeds only in regions of single strands of DNA. Topoisomerase, is the enzyme responsible for binding the double strand of DNA and separating each strand, forming two single strands, before the replication bubble arrives, only then can replication continue. For this reason, we can say that in the region of the chromosome marked as I, it will be necessary for the topoisomer to separate each strand of DNA for replication to proceed.

(a) Identify both the cellular component and the location of the component that is responsible for producing the luciferase protein from mRNAs transcribed in the plasmid-containing T lymphocytes. Explain what dictates to the lymphocytes the correct order in which amino acids should be linked to form the luciferase protein.

The mRNA which is read by the ribosome dictates the correct arrangement of amino acids through particular tRNA. The luciferase mRNA is moved to its similar protein in the ribosome which is seen in the cytoplasm of the cell. The chain of ribosome sits on the mRNA and forms a structure In the cytoplasm, called a polysome. this is useful in the fast synthesis of protein. The three-nucleotide genetic code in the mRNA which is being studied by the ribosome orders the right placement of amino acids through particular tRNA.

(a) Describe how the structure of a prokaryotic chromosome differs from the structure of a eukaryotic chromosome.

The structure of prokaryotic chromosome differs from the structure of eukaryotic chromosome by following ways: -A prokaryotic chromosome is shorter than the eukaryotic chromosome. -In prokaryotes, the circular chromosome is held in the cytoplasm in a region called nucleoid whereas in eukaryotes chromosomes are stored within a structure called the nucleus. -Prokaryotic chromosome comprises only a single origin of replication whereas the eukaryotic chromosome carries multiple origins of replication. -Prokaryotic chromosome consists of covalently closed (loop) circular DNA whereas the eukaryotic chromosome consists of linear DNA not circular.

(c) Identify the plasmid that must contain the CD3γ core promoter sequence but the fewest or no negative regulatory sequences. Based on the data in Figure 2, describe the most likely cause of the variation in luciferase activity among the cells that contain plasmids pCD3γ-419, pCD3γ-309, pCD3γ-239, and pCD3γ-199. Calculate the approximate percent increase in luciferase activity between cells containing plasmid pCD3γ-59 and cells containing plasmid pCD3γ-149. Round to the nearest whole number.

I HAVE NO IDEA

(d) Predict the most likely observed level of luciferase activity if plasmid pCDγ3-789 is introduced into nonlymphoid cells such as a line of kidney tissue cells. Provide reasoning tojustify your prediction.

Its level will be high because introducing plasmid into non lymphoid kidney tissue cell will most likely bring about blockages to the kidney tissue cell and its activities. Hence this is likely going to trigger the presence of luciferase to continually disintegrate the plasmid substances in order to promote smote flow of soluble substance's across the body

(c) Use the template of a replication fork to draw arrows that represent both continuous and discontinuous DNA synthesis. Draw one long arrow to show continuous DNA synthesis and three arrows to show discontinuous DNA synthesis. The arrows should point in the direction of nucleotide addition, and the three arrows showing discontinuous synthesis should be numbered 1, 2, and 3, in the order of fragment synthesis.

https://us-static.z-dn.net/files/d8c/74c8142b24792c373591f814b5976256.jpg