genetics

Question 1

cloning: group of identical cells/ organisms
species: group of organisms consisting of similar individuals capable of interbreeding

Answer 1

GEL ELECTROPHORESIS:
∙method of separating DNA fragments according to size
∙gel is made from agarose which has pores in its matrix
∙electric current applied. DNA (-vely) charged due to its phosphate groups so attracted to (+) electrode
∙small fragments migrate more easily through pores + travel further
∙fluorescent dye is added, binds to DNA

Question 2

ENZYMES:

1) nucleases- cut/shorten nucleic acid
2) ligases- join nucleic acid
3) polymerases- make copies of molecules
4) modifying enzymes- add or remove chemical group

Answer 2

Endonuclease’s (restriction enzymes):

sticky cutter- cut may be staggered with short single fragments either end

blunt cutter- cuts DNA between specific base sequences which enzyme recognises

Question 3

cloning DNA:
∙plasmid cut with restriction enzyme to open it
∙the gene is cut with the same restriction enzyme to ensure complementary sticky ends
∙join with H+ bonds forming recombinant DNA
∙DNA ligase inserted to join phosphodiester bonds of the two sections of DNA back together

Answer 3

expression vector: vector that is used for expressing a gene contained within the cloned DNA
(suitable host e.g. virus or bacteria)

gene library: total genomic DNA from a single organism. contains coding and non-coding sequence

cDNA: contains just coding sequence

colony hybridisation: method for the isolation of specific DNA sequences or genes from the bacterial cells containing hybrid DNA

Question 4

PCR (polymerase chain reaction):
∙using PCR a large number of copies of specific fragments of DNA can be made rapidly
∙requires: heat stable DNA polymerase, DNA primers 5-3
∙uses a machine called thermocycler which heats and cools DNA

Answer 4

denaturation: heat to 95 deg to seperate DNA strands by breaking through H+ bonds

primer annealing: cool to 50-60 deg to allow primers to attach to complementary bases

primer extension: heat to 70 deg to allow DNA polymerase to join complementary nucleotides

repeat 30-40 times

Question 5

DNA PRIMERS:
must be complementary
the longer the primer the more specific it is

Answer 5

SANGER SEQUENCING:
∙sequencing small fragments of DNA created by the use of restriction enzymes
∙DNA polymerase was used to synthesise complementary strands using PCR
∙4 PCR reactions are carried out ( one for each base). each contain normal and stop nucleotides
∙each PCR mix should generate all the possible terminating fragments for that base
∙fragments separated using gel electrophoresis
∙using fluorescent labelled primers, fragments can be defected by sequencing machines
∙read from bottom up, this method takes days but next-gen sequencing (NGS) takes hours

Question 6

APPLICATIONS OF THE DNA TECHNOLOGIES:
DNA profiling: requires hair sample or mouth swab to collect enough DNA which can be further amplified by PCR

genetically engineered products:
GM crops
vaccines for disease prevention

Answer 6

GMO’s (genetically modified organisms:
∙gene pharming
∙not wise to kill animals to extract proteins

∙cloning whole organism= dolly the sheep
(different sperm, different egg, different surrogate mother)

Question 7

EPIGENETICS:
∙refers to external modifications to DNA that turn genes on and off. They dont change DNA sequence, instead effect how cells read genes
∙can result in phenotype change without genotype change

Answer 7

k