48. Suppose a restriction enzyme recognizes the 6-base...

48. Suppose a restriction enzyme recognizes the 6-base sequence below in a double strand of DNA. Between which 2 nucleotides on each strand would the enzyme have to cut to produce a fragment with "sticky ends" that are indicated in the bases below? AAGCTT TTCGAA a. GC b. CT c. AA d. AG 49. To produce genetically engineered bacteria that make a human protein like Insulin, which of the following steps does a scientist have to take first? a. insert the human gene for the protein Insulin into a plasmid b. extract the protein from the bacterial culture that is making insulin c. use a restriction enzyme to cut out the gene from human DNA d. none of the above 50. One function of gel electrophoresis is to a. separate DNA fragments by weight b. cut DNA into fragment lengths c. recombine DNA with other genes d. extract DNA 51. Combining genes from different sources into a single DNA molecule is known as a. DNA fingerprinting b. PCR technique c. Vectoring d. Recombinant DNA technology 52. What is the advantage of producing transgenic plants? a. increasing herbicide resistance b. using more pesticides c. producing clones d. studying human genes 53. On an electrophoresis gel, Band B is closer to the positive end of the gel than is Band A. Which of the following statements is true? a. Band B is more positively charged than Band A b. Band B moved faster than Band A c. Band A is smaller than Band B d. Band B consists of larger DNA fragments than does Band A

Transcript

00:02 So you have a restriction enzyme recognize the six base sequence below.

00:08 A, a, g, c, t, t.

00:16 And then the bottom is t, t, c, g, a, a.

00:19 So the question says that between which two nucleotides on each strand would the enzyme have to cut to produce a fragment with sticky end that are indicated in the base below? so the correct answer is going to be c, between a and a.

00:33 So you can see when you cut between a and a, and then you'll produce a fragment a with a sticky end.

00:53 So this is the five prime end here and three there.

01:01 And then the other one is a, g, c, t, t with an a.

01:15 And this is the five prime end.

01:17 This is the three.

01:18 So you can see that you have a sticky end that protruding from the five prime and a, g, c, t.

01:26 So this is the sticky end produced by the enzyme cut.

01:31 So the correct answer is going to be c between a and a.

01:41 All right.

01:41 Second question.

01:44 To produce genetically engineered bacteria that make a human protein like insulin, which of the following step does scientists have to take first? so you want to produce a recombinant human protein in the bacteria.

02:02 The very first thing you will actually have to extract the rna of the human protein, human gene.

02:13 So you cannot directly use human gene to put them into plasmid.

02:20 This is because human are eukaryotic organism.

02:28 Eukaryotic genes has this process we call splicing.

02:33 During this process, the pre -mrna has certain sequence we call introns.

02:47 So they're junk sequences.

02:49 Somehow they have to be removed.

02:52 So introns will be cut out by splicing.

03:01 So in eukaryotic gene, you will have a longer pre -mrna.

03:06 But after splicing, you'll end up having a lot shorter sequence.

03:11 As you can see, the red part is intron.

03:15 After splicing, the intron will be removed.

03:18 You'll have a much shorter dna, sorry, mature mrna with two axons.

03:29 So this is a mature, mature mrna.

03:33 So the intron is being removed.

03:40 Now, this process doesn't happen in the prokaryotic gene organism.

03:55 So this means if we want to express a human protein in the bacteria cell, we cannot directly use human genomic dna.

04:05 And we also cannot extract the protein directly from the bacterial culture.

04:14 So the correct way to do is that we have to first of all extract the mature, mature mrna of the gene.

04:29 And then we convert the mature mrna into a cdna, which is double -stranded structure coming from the reverse transcription.

04:45 This is a process to convert the mrna into a dna, double -stranded dna.

04:52 So the cdna is an artificial dna created in the lab.

04:56 So the unique part of cdna is that it does not contain intron.

05:03 When you express cdna in the bacteria, it doesn't have to go through the splicing process.

05:10 But judging by all the option a, b, c, none of them is the correct answer because it says which of the step does the scientists have to do first? it should be extract the mature mrna.

05:24 So none of a, b, c is correct.

05:26 The correct answer is going to be d, none of above.

05:41 The next question.

05:43 So one function of gel electrophoresis is to, so obviously the gel electrophoresis main function is to separate dna fragment by their weight.

06:01 So the idea is that gel electrophoresis use agarose as a molecular sieve.

06:08 So the idea is that you have agarose gel, and then you have wells that you load your dna sample in it...

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