PCR is used to – DNA. It uses – to separate a DNA molecule, and then uses a(n) – to start – at a point selected by scientists. This technique can produce millions of – of a targeted DNA sequence.

The correct answer is - amplify, heat, primer, replication and copies.

Explanation:

Polymerase chain reaction is known as PCR. PCR is also known as a method that rapidly produce millions to billions copies of atargeted DNA sequence. It is widely used method for the separation of small DNA and amplify it to large amount to study by scientists.

So, the missing parts of the paragraph would be -

PCR is used to amplify DNA. It uses heat to separate a DNA molecule, and then uses a primer to start replication at a point selected by scientists. This technique can produce millions of copies of a targeted DNA sequence.

Thus, the correct answer would be -amplify, heat, primer, replication and copies.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).