LEts go paper 2 Flashcards
5 Examples of natural vegetative propagation?
Rhizomes Stolons/runners Suckers Tubers Bulbs
Rat sucks sausage to breathe
How do you produce a clone from a cutting?
Using scalpel take a cutting from end of stem from parent plant
Remove leaves from lower end of cutting
Dip lower end in rooting powder, that contains hormones that induce root formation
Plant cutting in a pot that contains growth medium
Provide cutting with warm and moist environment by putting plastic bag on it, or put in a propagator
How can you artificially clone plants using tissue culture?
Cells are taken from original plant that’s going to be cloned
Cells from stem and root tips used because they are stem cells, and can develop into any type of cell
Cells are sterilised to kill any microorganisms
Cells are placed on culture medium containing nutrients and growth hormones
Once cells have divided and grown into a small plant they are planted in soil
Will be genetically identical to the original plant
Steps in artificial embryo cloning for a cow (doesn’t matter which animal)?
An egg cell is extracted from a female cow and fertilised in a petri dish
The fertilised is left to divide at least once, forming an embryo in vitro (outside a living organism)
Individual cells from the embryo are separated and each is put into a separate petri dish, each cell divides and develops normally so an embryo forms in each petri dish
Embryos are implanted into female cows which act as surrogate mothers
Embryos develop in surrogate mothers and form offspring, all offspring genetically identical to each other
Steps in Somatic Cell Nuclear Transfer (SCNT) for sheep(again animal doesn’t matter)?
A somatic cell (any cell that isn’t a reproductive cell) is taken from sheep A. The nucleus is extracted and kept
An oocyte (immature egg cell), is taken from Sheep B, it’s nucleus is removed to form an enucleated oocyte.
Nucleus from sheep A is inserted into the enucleated oocyte, the oocyte from sheep B now contains genetic information from sheep A.
The nucleus and the enucleated oocyte are fused together and stimulated to divide via electrofusion (electrical current is applied) producing an embryo
The embryo is implanted into a surrogate mother and eventually a lamb is born that is a clone of sheep A.
What are the 3 main ways to immobilise enzymes?
Encapsulated in jelly like alginate beads, which acts as a semi permeable membrane
Trapped in a silica gel membrane
Covalently bonded to cellulose or collagen fibres
Describe the carbon cycle?
Carbon in form of CO2 in atmosphere is absorbed by plants when they carry out photosynthesis, becoming carbon compounds in plant tissues
Carbon passed on to animal consumers via feeding
All living organisms die and the Carbon compounds in the dead organisms are digested by micro organisms called decomposers, via saprobiontic feeding
Carbon returned to the air and water as all living organisms respire, including decomposers
However, if dead organic matter ends up in places where there aren’t any decomposers ( deep oceans or bogs), can be turned into fossil fuels ( heat and pressure over long time)
Carbon in fossil fuels released when they are burned = combustion
Other rocks formed from dead organic matter on sea floor, these rocks drawn down by tectonic plates, undergo chemical changes and release CO2, returned to atmosphere via volcanoes
Other rocks can also become land where they become chemically weathered and release CaCo3 ions into groundwater, which form the carbon containing rocks described above
Describe the Nitrogen cycle?
Nitrogen fixation:
When Nitrogen gas in the atmosphere is turned into ammonia by bacteria such as Rhizobium and Azotobacter. The ammonia can then be used by plants
Also gets into system via lightening or fertilisers
Rhizobium is found inside root nodules of leguminous plants
Mutulastic relationship with the plants, as they provide plants with Nitrogen compounds, and they provide them with carbohydrates
Azobacter is found in soil
Ammonification:
When nitrogen compounds from dead organisms are turned into ammonia by decomposers, which go on to form ammonium ions
Nitrification:
When ammonium ions in the soil are changed into Nitrogen compounds which can then be used by plants (Nitrates)
First nitrifying bacteria Nitrosomanas changed ammonium ions into Nitrites
Then Nitobacter turns Nitrites into Nitrates
Denitrification:
When Nitrates in the soil are converted into Nitrogen gas by denitrfying bacteria, as they use Nitrates in soil for respiration, under anaerobic conditions
Describe succession?
New species colonies land = the pioneer species
Abiotic condition are harsh as no soil, only specialised pioneer species can grow
Pioneer species changes abiotic conditions as they die decompose and form soil
Conditions less hostile and more organisms grow, more soil forms
Species become outcompeted as ecosystem becomes more complex and biomass increases
Reaches Climax community
What levels can gene expression (and therefore protein synthesis) be controlled at?
Transcriptional
Post-transcriptional
Post-translational
For an example of example of an operon, explain the lac operon in E.coli?
The lac operon has 3 structural genes which lacZ, lacY and lacA which produce proteins which allow the bacteria to digest lactose (including B-galactosidase and lactose permease)
Lactose not present:
The regulatory gene prodcues the lac repressor, which is a transcription factor which binds to operator site when there’s no lactose present. This blocks transcription because RNA polymerase can’t bind to the promoter
Lactose present:
When lactose is present, it binds to the repressor, changing the repressors shape so it can no longer bind to the operator site.
RNA polymerase can now begin transcription of the structural genes
What’s happens in transcription in relation to introns and exons?
Introns and exons are both copied into mRNA forming primary mRNA transcripts
Then in a process called splicing, the introns are removed and the exons join together, forming mature mRNA strands, this occurs in the nucleus
The mature mRNA then leaves the nucleus for the next stage of protein synthesis (translation)
How do hox genes control development?
Homebox sequences code for a part of the protein called the homeodomain
The homedomain binds to specific sites on DNA, enabling the protein to work as transcription factor
The protein binds to DNA at the start of developmental genes, activating or repressing transcription and so altering the production of proteins involved in the development of the body plan
What are the steps of apoptis?
Enzymes in the cell break down important cell components such as proteins in the cytoplasm and DNA in the nucleus
As the cell’s contents are broken down, it shrinks and breaks into fragments
The cell fragments are engulfed by phagocytes and digested
3 techniques to study genes?
The polymerase chain reaction (PCR)
Gel electrophoresis
Cutting out DNA fragments, using restriction enzymes
How can multiple copies of a DNA fragment be made, using PCR?
A reaction mixture is set up, containing the DNA sample, free nucleotides, primers and DNA polymerase
DNA mixture is heated to 90 degrees, to break the hydrogen bonds between the 2 strands of DNA
Mixture is then cooled to between 50 and 65 degrees, so the primers can anneal (bind) to the strands
Reaction mixture heated to 72 degrees so DNA polymerase can work
DNA polymerase lines up free nucleotides with alongside each template strand, complementary base pairing means new complementary strands are formed
2 new copies of the fragment of DNA are formed, and one cycle of PCR is formed
Explain electrophoresis steps
Row of wells is created at the end of some agrose gel, which is in a gel box/tank, with the wells nearest to the negative electrode
Add loading dye to each DNA sample, helps the sample sink to bottom of wells making them easier to see. Add a set amount of each DNA fragment solution to each well
Pass an electrical current through the gel, DNA fragments are negatively charged so will move towards the positive electrode.
Small DNA fragments will move faster and travel further, through the gel causing them to separate by size, turn power off when 2cm from end. Stain the DNA fragments
The bands of different DNA fragments will now be visible
How can restriction enzymes be used to cut out DNA fragements?
Some sections of DNA have palindromic sequences of nucleotides, these sequences consist of anti-parallel base pairs (base pairs that read the same in the opposite direction)
Restriction enzymes are enzymes that recognise specific palindromic sequences (known as recognition sequences) and cut (digest) the DNA at these places
Different restriction enzymes cut at different specific recognition sequences because the shape of the recognition sequence is complementary to an enzyme’s active site.
If recognition sequences are present at either side of the DNA you want, you can use restriction enzymes to separate it from the rest of the DNA
DNA sample is incubated with the specific restriction enzyme, which cuts the DNA fragment via a hydrolysis reaction
Sometimes cut leaves sticky ends (small tails of unpaired bases at each end of the fragment), as cut in a zig zag motion. Sticky ends can be used to anneal the DNA fragment to another piece of DNA, that has sticky ends with complementary sequences
In depth description of how first step of genetic engineering works?
DNA fragment containing the desired genes is isolated using restriction enzymes
In depth explanation how the second step of Genetic engineering works?In depth explanation how the second step of Genetic engineering works?
The DNA fragment is inserted into a vector DNA (Vector is something used to transfer DNA into a cell, eg. plasmids (small circular molecules of DNA in bacteria, or bacteriophages (viruses that infect bacteria))
The vector DNA is cut open using the same restriction enzyme that was used to isolate the DNA fragment that containing the desired gene. So the sticky ends of the vector are complementary to the sticky ends of the DNA fragment containing the gene
The vector DNA and DNA fragment are mixed together with DNA ligase
DNA ligase joins up the sugar-phosphate backbone of the 2 bits, = ligation
In depth explanation how the third step of genetic engineering works?
The vector with the recombinant DNA is then used to transfer the gene into the bacterial cells
If a plasmid vector is used, bacterial cells have to be convinced to take in the plasmid vector, and it’s DNA
Eg. suspension of bacterial cells is mixed with plasmid vector in a machine called an electroporator
The machine is switched on and an electrical field is created in the mixture, increasing the permeability of the bacterial cell membranes, and allows them to take in the plasmids, this is called electroporation
With a bacteriophage plasmid, the bacteriophage will infect the bacterium by injecting it’s DNA into it, the phage DNA then intergrates with the bacterial DNA
What’s somatic therapy?
Altering the alleles in body cells, particularity targeting the cells most affected by the disorder
Somatic therapy doesn’t affect the individuals sex cells, so any offspring could inherit the disease
What’s germ line therapy?
Altering the alleles in the sex cells, this means every cell of any offspring produced from these cells will be affected by the gene therapy and they won’t inherit the disease, currently illegal
How can DNA be sequenced using the chain-termination method?
The following mixture is added to 4 separate tubes:
A single stranded DNA template
Lots of DNA primers
DNA polymerase
Free nucleotides
Florescently labelled modified nucleotide, like a normal nucleotide, but once it’s added to a DNA strand no more bases can be added after that, (a different modified base is added to each tube A,T,C,G
The tubes undergo PCR which produces many strands of different length DNA, because each one terminates at a different point
The DNA fragments in each tube are separated by electropheresis, and visualised under UV light
The complementary base sequence can be read from the gel as smallest length is first and longest is last
(Have to flip to find sequence of original strand)
