AQA A-level Biology 7402 - Paper 2 - 13th June 2019

Replica plating is a technique used to show which bacteria (or whatever) have taken up the desired gene you inserted (in the plasmid). It relies on bacteria having at least two antibiotic resistant genes (at least in 1 of the most common contexts).

Here is the method - let me know if you dont understand any point :smile:

1. Donor DNA inserted into ONE of the antibiotic resistant genes in the plasmid, Antibiotic A. The plasmid has ANOTHER antibiotic resistant gene, Antibiotic B.

2. Plasmid is inserted into bacteria. Therefore, bacteria will be resistant to B but NOT resistant to A as translation disrupted.

3. A velvet stamp stamps the growth media and transfers this to the replica plate.

4. On the plate, Antibiotic A is added.

5. As a result, bacteria with DONOR DNA will be wiped out.

6. Therefore, as a replica was made, we can return to the original culture and select the bacteria that contains the donor DNA.

Original post by curlyyy

Thank you, that's really helpful :smile:

Also, what is replica plating, is that just in vivo cloning?

Reply 21

curlyyy

13

Thanks so much!!

There are a couple things I still don't quite get tho :/

1. What is this velvet stamp?
2. If the antibiotic destroys all the plasmids that have taken up the donor, then what's the point in doing it? I guess I don't understand point 6. How do we use the plate to identify the ones that have taken up the plasmid from the original plate?

Original post by GCSEStudent903

Replica plating is a technique used to show which bacteria (or whatever) have taken up the desired gene you inserted (in the plasmid). It relies on bacteria having at least two antibiotic resistant genes (at least in 1 of the most common contexts).

Here is the method - let me know if you dont understand any point :smile:

1. Donor DNA inserted into ONE of the antibiotic resistant genes in the plasmid, Antibiotic A. The plasmid has ANOTHER antibiotic resistant gene, Antibiotic B.

2. Plasmid is inserted into bacteria. Therefore, bacteria will be resistant to B but NOT resistant to A as translation disrupted.

3. A velvet stamp stamps the growth media and transfers this to the replica plate.

4. On the plate, Antibiotic A is added.

5. As a result, bacteria with DONOR DNA will be wiped out.

6. Therefore, as a replica was made, we can return to the original culture and select the bacteria that contains the donor DNA.

Reply 22

Kayyy30

12

Is this in our spec???

Original post by GCSEStudent903

Replica plating is a technique used to show which bacteria (or whatever) have taken up the desired gene you inserted (in the plasmid). It relies on bacteria having at least two antibiotic resistant genes (at least in 1 of the most common contexts).

Here is the method - let me know if you dont understand any point :smile:

1. Donor DNA inserted into ONE of the antibiotic resistant genes in the plasmid, Antibiotic A. The plasmid has ANOTHER antibiotic resistant gene, Antibiotic B.

2. Plasmid is inserted into bacteria. Therefore, bacteria will be resistant to B but NOT resistant to A as translation disrupted.

3. A velvet stamp stamps the growth media and transfers this to the replica plate.

4. On the plate, Antibiotic A is added.

5. As a result, bacteria with DONOR DNA will be wiped out.

6. Therefore, as a replica was made, we can return to the original culture and select the bacteria that contains the donor DNA.

Reply 23

GCSEStudent903

13

Original post by curlyyy

Thanks so much!!

There are a couple things I still don't quite get tho :/

1. What is this velvet stamp?
2. If the antibiotic destroys all the plasmids that have taken up the donor, then what's the point in doing it? I guess I don't understand point 6. How do we use the plate to identify the ones that have taken up the plasmid from the original plate?

1. Velvet - sticky surface? Allow bacterial plate to stick to it (don't get too bogged down by it being velvet specifically).
2. We make a replicate plate.

We take a plate.
We stamp it.
We get another copy of the same plate.
The second plate will kill the bacteria WITH our DNA.
So we go back to the original plate.

As the ones that died (on the second plate) have the DNA we inserted.

Why do we kill them? To see which ones have our DNA. As the ones with our DNA will not survive. We can't kill it straight up without making a replica, as we would no bacteria left to use!

We make 2 copies. One copy is to experiment on and see which ones have our DNA. The other one is for us to thus use.

Reply 24

GCSEStudent903

13

Yes!

It has been asked in old papers also - check AQA BYB2 papers.

Original post by Kayyy30

Is this in our spec???

Reply 25

bayanotbee

9

anyone have any tips for the 15 mark passage/application question?? im really bad at all “suggest why” questions and literally got 0/15 for that question in my mock

Reply 26

DysfunctionalMe

10

If anyone has access to the AS biology papers please could you send them to me? Thank you!

Reply 27

Indiacorden

7

is it worth learning hardy weinburg or is that v unlikely to come up as it was in the paper last year?

Reply 28

Kayyy30

12

I would say it’s worth learning because it’s a common thing. Just like how inheritance questions always come up each year, deffo do go over hardy Weinberg

Original post by Indiacorden

is it worth learning hardy weinburg or is that v unlikely to come up as it was in the paper last year?

Reply 29

Cooper.S

3

In terms of the structure of muscles (myosin/actin etc.) Do we need to know the names of the different lines and bands (screenshot)?

Thanks

Screen Shot 2019-06-10 at 12.52.56 pm.png

Screen Shot 2019-06-10 at 12.52.56 pm.png

Reply 30

jam1e

14

What would be the best way at this point to try and pull my overall biology grade up with this paper and paper 3? I completely flopped paper 1 and I'm unsure if I can fix this with my other two papers

Reply 31

Kayyy30

12

Yes absolutely! There’s been past questions on it

Original post by Cooper.S

In terms of the structure of muscles (myosin/actin etc.) Do we need to know the names of the different lines and bands (screenshot)?

Thanks

Screen Shot 2019-06-10 at 12.52.56 pm.png

Reply 32

Virolite

14

same g i need an A for my offers, paper 1 was calm but I neglected revision for paper 2 :confused:

Original post by jam1e

What would be the best way at this point to try and pull my overall biology grade up with this paper and paper 3? I completely flopped paper 1 and I'm unsure if I can fix this with my other two papers

Reply 33

jam1e

14

Original post by Virolite

same g i need an A for my offers, paper 1 was calm but I neglected revision for paper 2 :confused:

I only need a C, I 100% only got an E in paper 1, completely ruined it

Reply 34

Virolite

14

nah chill, the new spec grade boundaries will bring that to a C minimum. you just gotta maintain that grade over the next 2 papers and you're calm

Original post by jam1e

I only need a C, I 100% only got an E in paper 1, completely ruined it

Reply 35

jam1e

14

Original post by Virolite

nah chill, the new spec grade boundaries will bring that to a C minimum. you just gotta maintain that grade over the next 2 papers and you're calm

I got an E in the first, there’s no way I’m getting 2 B’s in paper 2 and 3. I’ve never gotten a B before i’m too slow for grades like that 😋

Reply 36

Jwall2019

4

Original post by Cooper.S

In terms of the structure of muscles (myosin/actin etc.) Do we need to know the names of the different lines and bands (screenshot)?

Thanks

Screen Shot 2019-06-10 at 12.52.56 pm.png

We learnt it at my school so I think so?

Reply 37

Virolite

14

"Gross and microscopic structure of skeletal muscle. The
ultrastructure of a myofibril."

Spoiler

Original post by Cooper.S

In terms of the structure of muscles (myosin/actin etc.) Do we need to know the names of the different lines and bands (screenshot)?

Thanks

Screen Shot 2019-06-10 at 12.52.56 pm.png

Reply 38

mileyyyy

2

Does anyone know whether we need to know the methods of the required practicals for paper 2 or are those in paper 3?

Reply 39

georgehsclark

6

Do we have to know how to do the Chi-Squared test?
in spec it says:
"Use of the Chi-squared test to compare the goodness of fit observed phenotypic rations with expected ratios."

AQA A-level Biology 7402 - Paper 2 - 13th June 2019

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