DNA Replication (SL IB Biology)

Which of the following statements about semi-conservative replication of DNA are correct? 

1. DNA polymerase always works in the same direction along a strand of DNA, in the 3′ to 5′ direction.
2. The action of DNA polymerase is followed by that of helicase.
3. One strand of original DNA remains in each daughter molecule; the other strand has been made from free nucleotides.
4. Crick and Watson proposed the hypothesis of semi-conservative replication, whereas experimental evidence was later provided by Meselson and Stahl.

During the process of semi-conservative replication of DNA, which activity, relating to bonding, does not take place?.

The laboratory technique of Polymerase Chain Reaction (PCR) takes advantage of the ability of polymerase enzymes to copy pieces of genetic material quickly and accurately. Which of the following are necessary for successfully conducting PCR in a forensic examination at a crime scene? 

1. An active sample of human DNA or RNA polymerase
2. Buffer solution
3. A sample of target DNA or RNA
4. Free nucleotides
5. Primer sequences

The shaded boxes in the diagram below (left) indicate DNA sequences called VNTRs from three different loci that were amplified (via PCR) from DNA found at a crime scene.

Each individual has a unique pattern of VNTRs in their genome. 

The diagram on the right shows DNA profiles of fragments amplified from the VNTR regions of four suspects.  

Which of these suspects was most likely at the crime scene?

Which of the following statements explains the separation of molecules in electrophoresis?

What is the correct order of events for the stages of PCR shown in the diagram?

If one molecule of DNA goes through 5 PCR cycles in the thermocycler, how many copies of that molecule of DNA will be produced?

What key feature of the genetic code makes it possible to transfer genes between species?

Which statement can not be concluded from the DNA profile shown?

Which of the following shows the appearance of the DNA strands that would result after two rounds of DNA replication? Note that the black strands represent DNA present in the original DNA molecule. The grey strands represent newly-synthesised DNA. 

A DNA profile was created for two genes in three individuals (A, B, and C).

Which of the following statements, relating to the images provided, are correct?

The relationship between DNA fragment length and distance moved through the gel is linear.

Fragment length is determined by the number of repeated DNA sequences in a sample. .

There is a percentage increase of 50 % between the distance moved by fragment Y and that moved by fragment X.

Some scientists were investigating the allele frequencies in a population of flies for a gene responsible for insecticide resistance.

They obtained DNA samples from a representative group in the population and then carried out PCR to amplify the DNA.

Scientists used the same restriction endonuclease on each sample before undertaking PCR, explain why.

DNA samples were taken from five individuals and analysed using gel electrophoresis to produce a DNA profile.  The DNA profile shows the results for a single gene.

What conclusions can be made from the profile shown in the image?