Genomes And Gene Technologies

Front 1

Why do we sequence genomes?

Back 1

-identify genes

-find out evolutionary relationships

-modelling the effects of changes to DNA/genes

-identifying genes that may cause disease

-analysis of the whole individual

Front 2

What is the structure of a nucleotide?

Back 2

-phosphate group

-deoxyribose sugar

-nitrogenous base

Front 3

What do the phosphate groups do to DNA?

Back 3

make it negatively charged

Front 4

What is a BAC?

Back 4

bacterial artificial chromosome

Front 5

How are clone libraries produced?

Back 5

-gene is placed into a BAC and transferred to e.coli cells

-as these grow many copies of sections are produced (clone libraries)

Front 6

What is a PCR?

Back 6

polymerase chain reaction

Front 7

What is the PCR used for?

Back 7

replicating short sequences of DNA, but not entire chromosomes

Front 8

Why are primer molecules added when DNA is replicated using a PCR?

Back 8

DNA polymerase cannot bind to DNA directly so uses primer molecules to bind

Front 9

How is DNA replicated using a PCR?

Back 9

-DNA sample mixed with free nucleotides and DNa polymerase

-mixture heated to 95 degrees which breaks H bonds

-primers added and allowed to anneal as temperature is decreased to 55 degrees

-temperature raised to 72 degrees which is the optimum for DNA polymerase

Front 10

Why is DNA Treated with dideoxynucleotides?

Back 10

stop any growing DNA chains and binds to end of individual strands

Front 11

Why are dideoxynucleotides tagged with a dye?

Back 11

they fluoresce a colour specific to the base

Front 12

What happens in electrophoresis?

Back 12

-different sized fragments of DNA are separated

-positive charge used to draw DNA towards an anode through a porous gel (e.g. agarose)

-shorter fragments travel faster than longer fragments

-fragments are passed through a laser which records the sequence of colours thanks to the dyes which is analysed and converted back to the triplet code

Front 13

What can DNA probes be used for?

Back 13

identifying fragments that contain specific sequences

Front 14

What is a DNA probe?

Back 14

short single stranded piece of DNA which is complementary to the section of DNA being investigated

Front 15

What three ways are DNA probes labelled?

Back 15

-radioactive marker

-fluorescent marker

-enzyme that catalyses a colour change

Front 16

What can probes be used for?

Back 16

-locate a specific gene

-identify the same gene on a variety of different genomes

-identify the presence or absence of an allele

Front 17

What is genetic engineering?

Back 17

-involves extracting genes from one organism or manufacturing genes to place in another organism

-results in the organism expressing to inserted gene in its phenotype

Front 18

What does it mean when an organism is described as transgenic?

Back 18

they have had genes transferred to them from another species

Front 19

What is recombinant DNA?

Back 19

DNA that consists of fragments from different organisms that have been artificially bonded together

Front 20

What are restriction enzymes (e.g. restriction endonuclease) used for?

Back 20

cutting DNA at places where specific base sequences occur and only at that place

Front 21

What is the term used to describe an the part of DNA where a restriction enzyme cuts?

Back 21

Restriction site

Front 22

What are the exposed bases called?

Back 22

sticky ends

Front 23

Where is recombinant DNA usually made?

Back 23

bacterial plasmids

Front 24

What is a vector?

Back 24

a means of transferring genes from one organism to another

Front 25

What is commonly used as a vector?

Back 25

-bacterial plasmids

-viruses

Front 26

How can bacterial plasmids be taken up by plant cells?

Back 26

bacterial plasmid is placed into a culture where plant cells are grown

Front 27

What process allows bacterial cells to exchange genetic material?

Back 27

bacterial conjugation

Front 28

What happens in bacterial conjugation?

Back 28

-tube called a pilus forms between donor and recipient

-restriction enzyme makes a cut on plasmid

-one strand of plasmid DNA is transferred to the recipient

-both cells synthesise new complementary strands

Front 29

How is human insulin-producing bacteria made?

Back 29

-mRNA that codes for insulin is identified in beta cells

-reverse transcriptase synthesises a complementary DNA strand

-DNA polymerase and free nucleotides are added to build the complementary strand , producing a copy of the original gene called cDNA

-unpaired nucleotides are added to create sticky ends on the cut plasmid

-plasmids cut open with restriction enzymes, dna fragment is senserted and sticky ends are sealed by ligase = recombinant DNA

-plasmids are mixed with bacteria, some take up the plasmids

-bacteria is grown on an agar plate

Front 30

Why is the making of human insulin-producing bacteria ineffective?

Back 30

-some bacteria may not take up the plasmid at all

-some bacteria may take up the plasmid but not seal it to its own plasmid

Front 31

How can genetic markers be used to identify bacteria that have taken up a recombinant plasmid?

Back 31

-original bacterial plasmids contain ampicillin and tetracycline resistant genes, e.coli is susceptible to both.

-DNA fragment is inserted in the middle of the tetracycline gene rendering it useless

-replica plating is used

i) bacteria grown on agar forming colonies

ii)samples are taken and then grown on ampicillin agar so only those who have taken up the plasmid will grow

iii)samples from those colonies are then transferred to tetracycline agar, those that haven't taken up insulin will continue growth

-colonies that have taken up insulin are then identified and transferred to a fermenter

Front 32

How is golden rice made?

Back 32

-psy gene from maize and crtl gene from soil bacterium are isolated using restriction enzymes

-inserted into a plasmid using restriction enyzme

-recombinant plasmid put back in bacterium

-rice cells are incubated with the bacteria which infects the rice plant cells. genes are inserted into the plant cells by the bacteria.

-golden rice!

Front 33

What is gene therapy?

Back 33

the use of genetic technology to treat genetic disorders

Front 34

What is somatic gene therapy?

Back 34

-engineering a functional copy of the gene into relevant cells with faulty copies so that the right protein is synthesised; or killing these cells by causing them to express antigens

Front 35

What is germline gene therapy?

Back 35

-modifications are introduced to the sex cells so the cells of the resulting zygote will contain the modification

Front 36

Compare somatic gene therapy and germline gene therapy.

Back 36

-S: allele introduced into target cells which must be extracted first

-G: allele is introduced into germline cells; easier delivery technique

-S: treatment is short lived and has to be repeated regularly, specialised cells will not pass on the allele in division and it is restricted to an individual

-G: all cells derived from the germline cell will have the allele

-S: hard to get allele into genome due to recipients immune system

-G: straightforward but ethical issues

Front 37

What is xenotransplantation?

Back 37

the transplantation of cell tissues or organs between animals of different species

Front 38

what is allotransplantation?

Back 38

the transplantation of cell tissues or organs between animals of the same species

Front 39

What are the problems of using a pig for xenotransplantation with humans?

Back 39

-organs are different sizes

-lifespan of pigs is shorter which will affect organs and tissues

-organ is adapted for aa different optimum enzyme temperature

-animal welfare concerns

-religious beliefs

-disease transfer

Front 40

What are the ethical issues with using microorganisms?

Back 40

-engineered microorganisms may escape and transfer genes (With unknown effects!) to pathogenic microorganisms

-antibiotic resistance genes are used as markers and may be passed on to other organisms

Front 41

What are the ethical issues with using plants?

Back 41

-less genetic variation

-genes may pass on to unwanted species and give them things like pesticide resistance which will disrupt biological communities

-modified plants may be toxic to organisms and cause an immune response from humans

-resistance may lead to he evolution of more dangerous pathogens

Front 42

What are the ethical issues with using humans and animals?

Back 42

-animal suffering

-religious beliefs

-effects of gene transfer are unpredictable

-fear of using technology to enhance favourable characteristics in offsrping