Polymerase Chain Reaction

What is the main goal of PCR?

To make millions of copies of specific DNA sequences

• usually tandem repeats so samples can be compared.

PCR is modeled after what natural biological process?

DNA replication

PCR was developed in which decade?

The 1980s

What type of DNA sequences are most commonly targeted in PCR for comparison?

Tandem repeats (such as STRs/SSRs)

Are most eukaryotic DNA sequences coding or non-coding?

Most are non-coding.

What are pseudogenes?

Mutated, non-functional copies of genes that persist in the genome as molecular fossils

What are endogenous viral sequences?

Viral DNA that became part of the genome after being reverse-transcribed during past infections and mutated into non-functional sequences.

What events can create non-coding DNA through errors?

Misalignments during crossing over.

What four main components are required for PCR?

• Template DNA

• dNTPs

• Primers

• Taq polymerase

What is the role of template DNA in PCR?

It is the sample that will be amplified

What are dNTPs used for in PCR?

They are the nucleotides used to build the new DNA strands.

Why must primers be specific to the STR or SSR in PCR?

Because primers determine exactly which region of DNA will be amplified

What is Taq polymerase and why is it used in PCR?

A heat-resistant DNA polymerase from Thermus aquaticus that can function at high temperatures (~70°C).

Why is heat resistance important for PCR enzymes?

PCR requires repeated heating cycles, so the enzyme must survive high temperatures.

Where was the organism that produces Taq polymerase found?

In hot springs (Thermus aquaticus)

What part of evolutionary history contributed to the abundance of non-coding DNA in eukaryotes?

Mutations and viral insertions accumulated over billions of years

Why are tandem repeats useful in comparing DNA samples?

They vary between individuals, making them good markers for identification.

What is the primary purpose of PCR?

A. To translate RNA into proteins
B. To make millions of copies of specific DNA sequences
C. To create plasmids inside bacterial cells
D. To repair damaged DNA

B. To make millions of copies of specific DNA sequences

PCR is modeled after which natural biological process?

A. Transcription
B. Translation
C. DNA replication
D. Gene expression regulation

C. DNA replication

PCR was developed in the:

A. 1960s
B. 1970s
C. 1980s
D. 1990s

C. 1980s

What type of DNA regions are most commonly amplified for comparing samples?

A. Exons
B. Promoters
C. Tandem repeats (STRs/SSRs)
D. Mitochondrial DNA

C. Tandem repeats (STRs/SSRs)

Most eukaryotic DNA is:

A. Protein-coding
B. Non-coding
C. Ribosomal
D. Viral

B. Non-coding

Which of the following best describes pseudogenes?

A. Functional copies of active genes
B. Viral genes inserted into bacteria
C. Non-functional, mutated copies of genes
D. Genes that code for tRNA

C. Non-functional, mutated copies of genes

Endogenous viral sequences originate from:

A. Env proteins that activate transcription
B. Viruses that were reverse-transcribed and inserted into the genome
C. Bacteria that infect the nucleus
D. Amplification errors in PCR

B. Viruses that were reverse-transcribed and inserted into the genome

Which genetic event can create new non-coding DNA regions?

A. Errors in transcription
B. Misalignments during crossing over
C. Dehydration of chromosomes
D. Polymerase ribosome collisions

B. Misalignments during crossing over

Which of the following is not required for PCR?

A. Template DNA
B. Primers
C. dNTPs
D. Ribosomes

D. Ribosomes

What is the function of primers in PCR?

A. To unzip DNA strands
B. To determine what DNA region gets amplified
C. To catalyze nucleotide formation
D. To stabilize Taq polymerase

B. To determine what DNA region gets amplified

What makes Taq polymerase suitable for PCR?

A. It works only at low temperatures
B. It binds to RNA instead of DNA
C. It can withstand high heat used during PCR cycles
D. It is slower but more accurate than other polymerases

C. It can withstand high heat used during PCR cycles

Taq polymerase comes from which organism?

A. E. coli
B. A plant chloroplast
C. Thermus aquaticus
D. Homo sapiens

C. Thermus aquaticus

Thermus aquaticus naturally lives in:

A. Deep ocean trenches
B. Hot springs
C. Arctic ice
D. Desert soil

B. Hot springs

Which component of PCR provides the building blocks for new DNA strands?

A. Primers
B. Template DNA
C. dNTPs
D. Helicase

C. dNTPs

Why do researchers compare tandem repeats (STRs)?

A. They are identical in all humans
B. They vary between individuals
C. They code for enzymes
D. They cannot mutate

B. They vary between individuals

Why is non-coding DNA useful for PCR analysis?

A. It mutates frequently and varies between individuals
B. It is protected from polymerases
C. It always codes for RNA
D. It is too large to change over time

A. It mutates frequently and varies between individuals

Which statement best describes the evolution of non-coding DNA in eukaryotes?

A. It formed only in the last 50,000 years
B. It accumulated through billions of years of mutations, viral insertions, and recombination events
C. It was created to regulate metabolic pathways
D. It is destroyed every few generations

B. It accumulated through billions of years of mutations, viral insertions, and recombination events