Can someone help me from question 7 to question 9? I got the following answers.

Question

Can someone help me from question 7 to question 9?

I got the following answers.

7) D

8) A

9) E

Please help, I don't want to fail this class so double checking my answers.

QUESTION 7 1 points Save Answe What happened in the Grilfith transformation experiment? O A smooth strain passed genetic information to a rough strain. 0 A rough strain passed genetic information to a smooth strain. A smooth strain underwent mutation to convert it to a rough strain. A rough strain underwent mutation to convert it to a smooth strain QUESTION 8 1 points Save Answer What is the difference between purines and pyrimidines? O Purines are found in RNA while pyrimidines are tound in DNA. Pyrimidines are tound in RNA while purines are found in DNA. Purines contain a double ring backbone, while pyrimidines contain a single ring backbone. O Pyrimidines contain a double ring backbone while purines contain a single ring backbone. QUESTION 9 1 points Save Answer Bacterial DNA replication is diferent from human DNA replication. From the choices below select the best reason why the replication mechanisms need to be different. O there are no lagging strands in bacteria 0 bacteria can't make Okazaki tragments humans have a bigger genome than bacteria the helicase enzyme is only found in one of the two organisms O enzymes in the two organisms work in opposite orientations

Explanation / Answer

7. Griffith in his experiment used two different strain of Streptococcus pneumoniae, (i) type III-S (smooth), and (ii) type II-R (rough). Type III-S is virulent as it forms a polysaccharide coat around it during infection, which protect them from the host’s immune system and cause hosts’ death. Type II-R is a non-virulent type as it does not form this polysaccharide coat. Griffith inject the heat-killed type III-S bacteria and the type II-R bacteria to the mouse, and it was observed that both strain fail to develop pneumonia in mouse. Surprisingly, when he mixed the two strains (heat-killed type III-S and type II-R) and injected to the mouse, he observed that this resulting strain is capable to develop pneumonia and cause death. From this experiment, he concluded that at DNA of the type III-S is not degraded due to the heat and this DNA is transferred to the type II-R bacteria, which make the non-virulent type II-R strain to a virulent strain. Therefore, the correct option is A: A smooth strain passed genetic information to a rough strain.

8. Purines are the nucleotide bases which contain double ring backbone. Adenine and Guanine are the purines. Pyrimidines possess single ring backbone, and thymine, cytosine and uracil are the pyrimidines. Both DNA and RNA are composed of these nucleotide bases. DNA double stranded backbone is formed by either the complementary pair of Adenine (A) – thymine (T) or the complementary pair of guanine (G) and cytosine (C). Unlike DNA, RNA contains uracil (U) instead of thymine (T). Therefore, the correct answer is C: purines contain a double ring backbone, while pyrimidine contain a single ring backbone.

9. Bacteria possess circular chromosome that contain single origin of replication from where replication starts. DNA polymerase moves at a speed of 100kb per minute, thus one round of DNA replication needs 40 mins in case of bacteria. The human genome is much larger in size than any bacterial genome, and the DNA forms highly compact structure called nucleosomes which is sequestered into multiple chromosome. Thus human DNA replication needs multiple origin of replication and the rate of replication movement is 2 kb per minute. These multiple origin of replication permit of the replication of specific regions of the genome at a specific time of S phase. After recognition and establishment of initiator protein complex at the site of origin of replication, unwinding of template DNA occurs in both bacterial and human DNA by different types of helicase. Thus, helicase is present in both bacteria and human cells. As DNA replication in both bacteria and human is bidirectional, thus, in both cases leading and lagging strand were generated. As lagging strand synthesis occurs in discontinuous manner, Okazaki fragments are formed during both bacterial and human DNA replication. The enzyme machinery which are involved in the DNA replication event in the bacteria and human possess significant differences in terms of sequences and structure and to some extent their mechanism. But it is not reported that the replication mechanism differs in bacteria and human due to the fact that these enzymes work in an opposite orientation. Thus, the option C: the human has a bigger genome than bacteria is correct.

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