BIO5101 Final Term Topics 91-109

BIO5101 (Introduction To Biotechnology) · Complete Note (Topic 091-109) · Topic 091: Inverse PCR

Inverse PCR (IPCR) is a variation of the basic PCR technique used to amplify unknown DNA

sequences flanking a region of known sequence.

Useful when standard PCR primers cannot bind to unknown regions.

Starts with a restriction fragment of DNA digested by a restriction enzyme.

The DNA fragment contains a known region (used to design primers) and an unknown flanking

region (target of amplification).

Circularization of the DNA fragment allows primers to amplify regions outward from the known

sequence.

A second digestion may linearize the circular DNA to position primers correctly for amplification.

Allows analysis of flanking sequences such as promoters, regulatory elements, or insertion sites.

o Digest genomic DNA with a restriction enzyme to generate sticky ends.

o Circularize the DNA fragment using ligase.

o Digest with a second restriction enzyme (if necessary) to linearize circular DNA at a known

region.

o Design primers from the known region.

o Perform PCR amplification to obtain the unknown flanking sequence.

o Sequence amplified product for analysis.

o Identify sequences adjacent to transposons or viral integration sites.

o Study gene regulatory regions.

o Map unknown flanking sequences in genomic DNA.

o Detect insertion sites of transgenes in GM organisms. o Requires knowledge of one DNA region to amplify adjacent unknown sequences.

o Circularization is key to inverting the target sequence for PCR.

o Widely used in genomics, molecular biology, and genetic engineering.

Q1. What is the main purpose of inverse PCR?

A1: To amplify unknown DNA sequences flanking a region of known sequence.

Q2. Why is circularization necessary in inverse PCR?

A2: Circularization allows primers to bind to the known region and amplify sequences outward, which

would not be possible in linear DNA.

Q3. Give an example of an application of inverse PCR.

A3: Mapping viral integration sites or identifying flanking regions of transgenes in genetically modified

organisms.

Q1. Explain the steps involved in inverse PCR.

A1:

o Digest DNA with a restriction enzyme to generate fragments.

o Circularize DNA fragments using ligase.

o Optional second digestion to linearize DNA at a known region.

o Design primers from the known sequence.

o Amplify unknown flanking region via PCR.

o Analyze amplified sequence for genetic or genomic studies.

Q2. How does inverse PCR differ from standard PCR?

A2:

o Standard PCR amplifies between two known primers.

o Inverse PCR amplifies unknown regions adjacent to a known sequence using circularized DNA

and primers from the known region.

Q3. Describe an application of inverse PCR in genetic research.

A3:

o Identify transposon insertion sites in a genome.

o Amplify promoter or regulatory regions adjacent to known genes. o Study integration of viral DNA into host genomes.

o Inverse PCR is used to amplify:

1. a) Known DNA sequences

2. b) Unknown flanking DNA sequences

3. c) RNA sequences

4. d) Proteins

o Circularization in inverse PCR is necessary to:

1. a) Sequence DNA directly

2. b) Allow primers to amplify flanking regions

3. c) Digest DNA

4. d) Bind antibodies

o The known DNA region in inverse PCR is used to:

1. a) Design primers

2. b) Digest RNA

3. c) Form proteins

4. d) Label DNA

o Which enzyme is used for circularization?

1. a) DNA polymerase

2. b) Ligase

3. c) Restriction enzyme only

4. d) RNase

o Inverse PCR helps study:

1. a) Flanking sequences of genes

2. b) Protein folding

3. c) Carbohydrate metabolism

4. d) Lipid biosynthesis

o A second digestion in inverse PCR is used to: