Harford Community College BIO 120 General Biology I DNA Barcoding Week 1 Assignm
ID: 145745 • Letter: H
Question
Harford Community College BIO 120 General Biology I DNA Barcoding Week 1 Assignment Name: Date: 1. During the DNA extraction procedure, which of the following helped to disrupt the cellular membranes and break open the cells? Circle all that apply: a. Grinding the tissue sample with a pestle b. Lysis solution C. Silica resin d. PCR primers e. Tris-HCI buffer 2. The purpose of PCR is to a. Denature DNA b. Purify DNA c. Amplify DNA d. Separate DNA Describe the three steps that take place in each cycle of PCR. What happens in each step? 3. 4. What does the term "amplify" mean in this lab?Explanation / Answer
1. The correct options are:
a. Grinding the tissue sample with a pestle.
b. Lysis solution.
Silica gel is used for DNA adsorption. PCR primers are used to bind denatured DNA to start amplification. Tris-HCl buffer is used as a general buffer during the experiments.
2. The correct option is c. Amplify DNA. This is the ultimate goal of PCR. However denaturation is the first step of PCR to achieve amplification.
3. PCR (polymerase chain reaction) is performed in many cycles. Each cycle consists of major three steps:
Denaturation: the double stranded DNA sequence is heated at ~94°C to separate the two strands of DNA (resulting in single stranded DNA).
Annealing: Complementary PCR primers binds to stranded DNA when the single stranded DNA is cooled at ~53°C (~5-10 °C lower than the melting temperature of DNA). The PCR primers provide starting point for new strand synthesis by DNA Taq polymerase enzyme.
Extension: Taq polymerase uses single stranded DNA as template and synthesise new complementary strands in 5'->3' direction. The temperature was kept ~72°C during extention.
After extention, one cycle is complete resulting in doubling of DNA sequences. Such cycle is run until desired amplification is obtained.
4. Amplify means to increase the number of copy. More specifically, it refers to make the a number of copies from a single DNA sequence.
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