Unit 1 KA2

Question 1

DNA replication

Answer 1

Parent DNA molecules are copied exactly so that genetic information can be passed to daughter cells via mitosis.

Question 2

DNA polymerase

Answer 2

Enzyme involved in DNA replication.

It adds nucleotides to the 3’ end of an existing nucleotide strand (eg. a primer)

Question 3

Replication fork

Answer 3

The point at which the 2 template strands of DNA separate.

Question 4

Primer

Answer 4

A short nucleotide strand, which binds to the template strand to initiate DNA replication.

Question 5

Template strands

Answer 5

The original DNA molecule that is to be copied.

There are 2 template strands - which are copied to produce the leading and lagging strands.

Question 6

Leading strand

Answer 6

This is produced continuously from the 3’ end by DNA polymerase, working towards the replication fork.

Question 7

Lagging strand

Answer 7

The DNA strand that is produced in fragments. (discontinuously)

The template strand is primed in sections, and nucleotides are added away from the replication fork, to the 3’ ends of the primers, using DNA polymerase.

The fragments are joined by ligase.

Question 8

DNA ligase

Answer 8

An enzyme which joins the fragments of the lagging strand.

Question 9

Replication bubble

Answer 9

Many replication forks operate simultaneously, creating replication bubbles.

Question 10

Semi-conservative replication

Answer 10

he parent DNA strand separates, and each half acts as a template strand for the 2 daughter DNA molecules, which each contain half original and half new DNA.

This theory of replication was proved to be correct by Meselson and Stahl.

Question 11

Isotope

Answer 11

An atom containing extra neutrons, which makes it heavier than normal.

Question 12

PCR

Answer 12

Polymerase chain reaction.

A lab technique used to amplify DNA.

Primers are designed to target specific sequences to be amplified.

Used in forensic investigations to increase the size of a DNA sample for analysis.

Question 13

Amplify

Answer 13

To make bigger.

DNA samples are amplified using PCR.

Question 14

In vitro

Answer 14

‘In glass’ (ie. in a laboratory situation)

Question 15

Thermal cycler

Answer 15

A specialised water bath that can rapidly raise and lower temperatures during a PCR cycle.

Used with heat tolerant DNA polymerase to make the PCR process faster and more efficient.

Question 16

DNA profiling

Answer 16

DNA samples are amplified using PCR, are cut with restriction enzymes and are then separated using gel electrophoresis to create a unique ‘DNA fingerprint’ or genetic profile of an individual.

This can be compared to other DNA profiles eg. on a DNA database.

Question 17

Gel electrophoresis

Answer 17

A mixture of DNA fragments (that have been cut using restriction enzymes) is loaded into a well in a special gel.

An electric current is applied, and DNA moves through the gel towards the positive electrode, as it is negatively charged. Fragments are separated by size - the heaviest are dropped first.

The pattern created is a genetic profile.

Can also be used to separate proteins.

Question 18

Restriction enzyme (endonuclease)

Answer 18

An enzyme that is used to cut DNA at a specific sequence.

There are many different types which recognise different base sequences and therefore cut in different places.