Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    2
    ReputationRep:
    I have loads of past paper questions that I don't understand from Unit 4 and 5. Please can someone help by starting to explain HOW you work out the answer for these two questions about the Polymerase Chain Reaction?

    1) How many DNA molecules will have been produced from one molecule of DNA after 6 complete cycles?

    And this is a different question from a past paper:

    2) One cycle of the polymerase chain reaction takes 5 minutes to complete. Starting with a single gene, calculate the number of copies of the gene produced in 40 minutes.

    I have seen two different formulas used to work PCR questions out. One of them is 2^n where n is the number of cycles. Another is 2^n+1 where n is also the number of PCR cycles. I am very confused about which to use.
    •  Official Rep
    Offline

    15
    ReputationRep:
     Official Rep
    Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

    You can also find the Exam Thread list for A-levels here and GCSE here. :dumbells:


    Just quoting in Puddles the Monkey so she can move the thread if needed
    Spoiler:
    Show
    (Original post by Puddles the Monkey)
    x
    Offline

    0
    ReputationRep:
    Use 2^n. You know that through PCR, 1 DNA strand splits into 2, these 2 split into 4, 4 into 8 so on and so forth. By the time you get to 8, the DNA strand has been through 3 PCR cycles. And 2^3 is 8. When 8 splits into 16, it'll be 4 PCR cycles. 2^4 = 16.

    Hope I was of help.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by branteo97)
    Use 2^n. You know that through PCR, 1 DNA strand splits into 2, these 2 split into 4, 4 into 8 so on and so forth. By the time you get to 8, the DNA strand has been through 3 PCR cycles. And 2^3 is 8. When 8 splits into 16, it'll be 4 PCR cycles. 2^4 = 16.

    Hope I was of help.
    Thanks so muchhhh! That really makes sense!
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you like to hibernate through the winter months?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.