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QLDBiologyQuick questions
Unit 4: Heredity and continuity of life
Quick questions on PCR, gel electrophoresis, recombinant DNA, GMOs and CRISPR (QCE Biology Unit 4)
13short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is purpose?Show answer
Amplifies a specific DNA region from a tiny starting sample to billions of copies in a few hours.
What are components?Show answer
Template DNA, two primers (each 18 to 22 bases long, complementary to sequences flanking the target), the four dNTPs, a heat-stable DNA polymerase (Taq, from the hot-spring bacterium Thermus aquaticus), buffer with Mg2 plus ions, and a thermal cycler.
What are applications?Show answer
Forensic DNA profiling, paternity testing, prenatal genetic screening, diagnosis of bacterial and viral infections (including the SARS-CoV-2 RT-PCR test, where reverse transcriptase converts RNA to cDNA first), conservation genetics, ancient DNA studies.
What is application: recombinant insulin?Show answer
The human insulin gene is inserted into E. coli, which transcribe and translate it to produce human insulin in industrial fermenters. This replaced pig and cow insulin in the 1980s.
What is definition?Show answer
Organisms that carry a foreign gene introduced by recombinant DNA technology. The foreign gene is often called a transgene.
What is origin?Show answer
Adapted from a bacterial adaptive immune system that captures viral DNA fragments and uses them as guides to cut viral DNA on re-infection.
What are concerns?Show answer
Off-target edits, germline editing in humans (ethics), uneven global regulation.
What is dNA sequencing?Show answer
Sanger sequencing (chain-termination) for short reads; next-generation sequencing (Illumina, Oxford Nanopore) for whole genomes.
What are microarrays?Show answer
Detect the expression of thousands of genes simultaneously.
What is reverse transcriptase PCR?Show answer
Converts RNA to cDNA, then amplifies. Used for RNA viruses and gene expression analysis.
What is q1?Show answer
Describe the three steps in one PCR cycle and state the typical temperature for each. [3 marks]
What is q2?Show answer
A gel shows ladder bands at 200, 500, 1000, 2000 bp. A sample lane has a single band slightly above the 500 marker. Estimate the PCR product size and explain how the ladder calibrates the gel.
What is q3?Show answer
Refer to CRISPR-Cas9. (a) Identify the components needed to edit a target gene. (b) Explain one ethical consideration in human germline editing.