Unit 1: Genome Mapping

Question 1

what is a physical map?

Answer 1

determines the order of genes on each chromosome and the physical distance between them in terms of number of base pairs

Question 2

what is a genetic linkage map?

Answer 2

based on a frequency of recombination between two markers

Question 3

what are cloning vectors?

Answer 3

used as a way of maintaing DNA fragments so that they are easily identified and retrieved

Question 4

why is the same restriction enzyme used?

Answer 4

to produce fragments with ‘sticky ends’ to facilitate the placement of the fragment into the plasmid

Question 5

what type of bacterium stores fragments?

Answer 5

E.coli bacterium

Question 6

what are the stages of chromosome walking?

Answer 6

1. probe complementary to 3’ end of the marker sequence is synthesised and a radioactive or fluorescent label is attached to it
2. labelled probe is used to screen one of the DNA libraries
3. clone isolated carrying DNA sequence that hybridises to the probe
4. second probe prepared from 3’ end of cloned sequence
5. new probe is used to screen other library and pick out overlapping segment
6. steps are repeated until array of overlapping segments are produced