biochem 6. Genetic Testing

Assuming there is one copy of the target DNA sequence before PCR, how many copies of DNA are there after 5 PCR cycles? 256 6 65,536 16 32

32 Each cycles double the numbers of DNA copy. Round 1: 1->2. Round 2: 2 ->4. Round 3: 4 -> 8. Round 4: 8 ->16. Round 5: 16 ->32.

DNA polymerase can synthesize new DNA strands in which direction? 3' to 5' 5' to 3' any direction N-terminus to C-terminus

5' to 3' DNA needs a free 3' end to bind to and initiate synthesis of a DNA. It synthesizes in a 5' to 3' direction.

You are designing a piece of DNA for a project and must select the appropriate nitrogenous bases. Which combination of nitrogenous bases would you find most suitable for your work? Thymine, Uracil, Adenine, Cytosine Adenine Guanine, Uracil and Thymine Adenine, Guanine, Thymine, Cytosine Adenine, Thymine, Cytosine, Uracil

Adenine, Guanine, Thymine, Cytosine

Which ingredients/molecules (at least four) are required to set up a polymerase chain reaction? DNA polymerase Amino Acids DNA nucleotides RNA nucleotides Template DNA Primers Ribosomes tRNA Ligase

DNA polymerase DNA nucleotides Template DNA Primers In PCR, a DNA sample is separated into single strands and incubated with DNA polymerase, deoxynucleotides (dNTPs), and two short DNA primers whose sequences flank the DNA segment of interest and thus define the region to be amplified. Recall from the section on DNA replication that DNA polymerase needs a primer to begin DNA synthesis. This requirement means the primers will direct the DNA polymerase to only synthesize complementary strands of the target DNA.

Which of the following steps in PCR occurs first? Elongation Denaturation Annealing Cycling

Denaturation Denaturation separated the DNA strands. The DNA strands must be separated to expose the bases to which the primers will bind.

The following are steps involved in a polymerase chain reaction. Which is the correct order: Elongation, denaturation, and annealing Denaturation, annealing, and elongation Annealing, elongation, and denaturation Elongation, annealing, and denaturation

Denaturation, annealing, and elongation PCR uses repeated cycles of temperature to amplify particular DNA segments. In the first step, the reaction mixture is heated to separate the DNA strands (denaturation). The reaction is then cooled to allow the DNA primers, which define the sequence to be amplified, to anneal (base pair) with the template DNA. In the third step, DNA polymerase extends the DNA primers to create a copy of the target DNA sequence. Heating the reaction to stop polymerization and separate the DNA strands starts the cycle over again

Which of the following changes can NOT be detected using PCR? Differences in DNA sequence Epigenetic changes Deletions Insertions

Epigenetic changes Epigenetic changes do not affect the sequence of the DNA. PCR is used to look at the DNA sequence

DNA ligase is a protein that connects primers to the template strand during PCR. True False

False In DNA replication, RNA primers are used at several places along the two strands of DNA, which means the new DNA is created in fragments (known as Okazaki fragments for the person who discovered them). However, RNA is much less stable than DNA, and needs to removed to prevent degradation. As each Okazaki fragment is finished, the RNA primer is removed by RNase H and replaced with DNA by DNA polymerase. This process leaves nicks in the sugar-phosphate backbone of the DNA. DNA ligase seals the nicks to create a continuous strand of new DNA.

Unlike DNA replication, in PCR, Okazaki fragments are used as primers. True False

False Okazaki fragments are involved in DNA replication, not PCR.

The polymerase chain reaction is a tool used to study protein structure. True False

False PCR is a tool used to amplify a specific segment of DNA.

Template DNA is broken down into fragments prior to being copied. True False

False The template DNA is never broken in in the process of PCR or DNA replication.

Which of the following components is NOT used in PCR? DNA template DNA nucleotides RNA polymerase Primers

RNA polymerase PCR makes a DNA copy, so DNA polymerase is used.

A thermocycler is a machine used for PCR that varies the temperature of a sample. True False

True

PCR could be used to identify a patient's susceptibility for developing breast cancer, for example by identifying mutations in the BRCA1 gene. True False

True

DNA polymerase is used in DNA replication and in PCR. True False

True Both PCR and DNA replication require DNA polymerase to make new copies of DNA.

Primers initiate replication in dividing cells. True False

True Primers are used as "handles" for DNA polymerase to grab onto as it starts to synthesize a new DNA strand.

A primer creates a "handle" for DNA polymerase to grab onto in order to synthesize a copy of the DNA. True False

True Primers provide a free 3' end ('handle") for DNA polymerase to grab on to, allowing for DNA polymerase to begin synthesis in the 5' to 3' direction.

dNTPs are DNA nucleotides used in PCR. True False

True dNTPs stands for deoxynucleotide triphosphates, which are the nucleotides used in DNA synthesis.