Date | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ1.9 |
Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
Command term | Outline | Question number | 9 | Adapted from | N/A |
Question
The cladogram is based on a comparison of open reading frames in DNA taken from fungi. It is an example of how open reading frames can be used in phylogenetic studies.
Outline how open reading frames are identified in DNA.
Explain what the branching off points represent in the cladogram of these fungi.
There are several methods of introducing DNA into a cell in the laboratory. Outline the introduction of recombinant DNA in plant cell protoplasts.
Markscheme
a. identify a start codon and stop codon
b. identify base sequences for a gene/that could code for a polypeptide
c. possible correlation with existing open reading frames in databases
a. represent common ancestors shared by the organisms that emanate from the point
b. indicates time since divergence
c. indicates number of differences in DNA
a. plant cells made into protoplasts by removing their cell wall / use cellulase to produce protoplasts
b. physical methods such as electroporation /microinjection/biolistics
c. chemical methods such as liposomes/calcium chloride/polyethylene glycol «PEG»
d. vectors such as Agrobacterium/tobacco mosaic virus